bmj open · smoking (which was rare) had no apparent hypertension effect. among males, regular...

For peer review only

Health-risk factors and the incidence of hypertension: 4-year prospective findings from a national cohort of 60,569

Thai open university students

Journal: BMJ Open

Manuscript ID: bmjopen-2013-002826

Article Type: Research

Date Submitted by the Author: 06-Mar-2013

Complete List of Authors: thawornchaisit, prasutr; Faculty of Health Sciences, School of Medicine; Lerdsin Hospital, Medicine de Looze, Ferdinandus; Faculty of Health Sciences, School of Medicine

Reid, Christopher; Monash University, School of Public Health and Preventive Medicine Seubsman, Sam-ang; Sukhothai Thammathirat Open University, School of Human Ecology Sleigh, Adrian; The Australian National University, National Centre for Epidemiology and Population Health

<b>Primary Subject Heading</b>:

Epidemiology

Secondary Subject Heading: Epidemiology, Public health

Keywords: Hypertension < CARDIOLOGY, General diabetes < DIABETES & ENDOCRINOLOGY, Risk management < HEALTH SERVICES ADMINISTRATION & MANAGEMENT, Adult nephrology < NEPHROLOGY

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Health-risk factors and the incidence of hypertension: 4-year prospective findings

from a national cohort of 60,569 Thai open university students

Prasutr Thawornchaisit, School of Medicine, Faculty of Health Science, University of Queensland, 288

Herston Road, Herston, Brisbane, QLD, 4006 Australia and Department of Medicine, Lerdsin Hospital,

Silom road, Bangrak, Bangkok, 10500 Thailand

Email: [email protected]

Telephone: 662-585-8015

Fax: 662-912-0121

Prasutr Thawornchaisit, MD, MPH1, Ferdinandus de Looze, MBBS, MSc1, Christopher M Reid, PhD2, Sam-

ang Seubsman, PhD3, Adrian Sleigh, MD4, Thai Cohort Study Team*

1 School of Medicine, University of Queensland, Brisbane, Australia, 2 School of Public Health and

Preventive Medicine, Monash University, Melbourne, Australia, 3 School of Human Ecology, Sukhothai

Thammathirat Open University, Nonthaburi, Thailand, 4 National Centre for Epidemiology and Population

Health, ANU College of Medicine, Biology and Environment, The Australian National University,

Canberra, Australia.



Key words: hypertension; socioeconomic status; body mass index; smoking, drinking

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Article summary

Article focus

To evaluate the role of health-risk factors in 2005 Thai Cohort Study (phase I) such as age, personal income,

educational attainment, obesity (body mass index), physical activity, diabetes mellitus, kidney diseases, high

lipids, cigarette smoking and alcohol consumption in the development of hypertension in phase II of the

Thai Cohort Study 2009.

Key Messages

Overall, the incidence of self-reported hypertension in Thai adults was 3.5% and the rate in males was more

than twice the corresponding rate in females (5.2% vs. 2.1%).

Marriage or having a partner increased the risk of hypertension in females but not in males. Planned

exercise, averaged across the 4-year follow-up, was protective for males. In males, higher LPPA (≥15

sessions / week) associated with lower incidence of hypertension however this was not observed in females.

In males, current-smokers had a higher risk of developing hypertension than non-smokers while in females,

smoking (which was rare) had no apparent hypertension effect. Among males, regular drinking increased the

risk of incident hypertension

Strengths

In Thailand, this cohort constitutes the largest study to examine the longitudinal effect of most health-risk

factors on hypertension development. The influence of risk factors on hypertension incidence is clearly

demonstrated since this is a large longitudinal cohort covering a 4-year period. As a consequence, the

independent risk factors for hypertension in Thais can be identified.

Our cohort represents Thais well in geography and socio-economy so the results reflect the trend of health-

risk transition in the Thai population.

Limitations

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However, our study has limitations since it relied on self-report. There may be recall and reporting errors.

Because of the better education attainment of STOU students combined with their representative income and

geographical location, they represent the next generation of Thais.

Abstract

Objective

As Thailand is transitioning from a developing to a middle-income developed country, chronic diseases

particularly cardiovascular disease have emerged as major health issues. Hypertension is a major risk factor

for heart attack and stroke and earlier cross-sectional studies have indicated that the prevalence is increasing.

This study evaluates the impact of a number of demographic and lifestyle related health risk factors on the

incidence of hypertension over a 4-year period.

Designs

This 4-year prospective study analysed the health-risk factors and their effects on incidence of hypertension

in the national Thai Cohort Study (TCS) from 2005 to 2009. 56,072 Sukhothai Thammathirat Open

University students who participated in both 2005 and 2009 questionnaire surveys and who were

normotensive in 2005 were included in the analysis. Adjusted relative risks of association between each risk

factor and incidence of hypertension were calculated by sex, after controlling for the confounding factors

such as age, SES, BMI and underlying diseases.

Results

The overall 4-year incidence of hypertension was 3.5% with the rate in men being remarkably higher than

that in women (5.2% vs. 2.1%). Hypertension associated with age, a higher BMI and having co-morbidities

in both sexes. In men, hypertension associated with physical inactivity, smoking, alcohol and fast food

intake. In women, hypertension was only related to having a partner.

Conclusion

In both men and women, hypertension was highly associated with age, obesity and co-morbidities while it

had no association with socio-economic factors. The cohort pattern of socio-economy and hypertension

reflects that the health-risk transition in Thais is likely to be at the middle stage. Dietary and lifestyle factors

are associated with the incidence of hypertension in Thais and may be amenable targets for community

based hypertension control programs.

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Introduction

Hypertension is a global public health challenge due to its high prevalence and the concomitant increase in

risk of stroke and cardiovascular diseases [1]. In 2007, according to the World Health Organization,

cardiovascular diseases caused 33.7% of all deaths in the world, while other chronic diseases were

responsible for 26.5% [2]. Globally, it has been estimated that premature deaths resulting from hypertension

annually are approximately 7.1 million, which account for 64 million disability-adjusted life years (DALYs)

[3]. Hypertension ranks third, after underweight and unsafe sex, of the six major risk factors contributing to

the global disease burden[3].

In Thailand, hypertension is the third major risk factor of the national disease burden and causes 600,000

DALY losses per year [4]. The prevalence of hypertension has been estimated from a number of cross-

sectional studies among adults and has been increasing over the past decades from 20% in 1985 to 22% in

2004 [4-6]. The emergence of hypertension has been the result of rapid socioeconomic development which

has resulted in one third of Thais migrating to urban areas [7]. Urbanization has been associated with

increased obesity as people become less physically active and adopt sedentary life styles such as spending

more time watching television, sitting and using computers [7 8]. These factors, in association with

Thailand’s ageing population [9], underpin the importance of controlling hypertension in Thai community.

As there is limited longitudinal research on health risk factors and hypertension incidence in Thailand [5].

The purpose of this study is to address that knowledge gap. We prospectively examined the influence of a

cluster of health-risk factors on the incidence of hypertension during 4 years of follow-up in the Thai Cohort

Study (TCS). This large national cohort of Thai adults has been followed since 2005 for risk factor trends

and associated disease outcomes, including hypertension.

Methods

Study population

The first TCS evaluation was conducted in 2005 by sending twenty-page health-risk questionnaires to the

200,000 distance-learning students enrolled at Sukhothai Thammathirat Open University (STOU) and

87,134 (44%) completed them and signed the consent forms. The cohort has been shown to be socio-

economically and geographically well representative of the Thai population [10]. However, they resided

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more in urban areas (51.8% vs. 31.1%) and on average were younger and better educated than most Thai

adults. Details of the baseline TCS methodology have been published [10]. This questionnaire focused on

socio-demography, habitation, work, health services, injury, sedentary habits, physical activity, transport,

underlying diseases, family history, personal behaviours, BMI, and consumption of foods, vegetables and

fruit. A 4-year follow-up was carried out in 2009. Overall, 71% of the cohort responded generating

longitudinal data on 60,569 participants.

Incident Hypertension

Incident hypertension was defined as being normotensive in 2005 and self-reported hypertensive in 2009.

Hypertension incidence was the dependent variable for analyses and the person-time denominator included

all individuals at risk - those 57,558 participants with longitudinal data who were negative for hypertension

in 2005, the beginning of the 4-year study period.

Risk Factors

Participants were grouped into three age categories: younger (≤30 years), middle (31-40 years) and older

(>40 years). Urbanization status was based on rural (R) or urban (U) residence, first when aged 10-12 years

old and again in 2005, producing four groups: lifelong ruralites (RR), urbanizers (RU), de-urbanizers (UR)

and urbanites (UU). Personal monthly income was divided into four categories: ≤7000 baht, 7001–10000

baht, 10001–20000 baht and >20000 baht. In 2005, one US dollar was equivalent to 42 baht so most of

participants had quite low incomes. Household assets were classified into three categories: low (≤30,000

baht), medium (30,001-60,000) and high (>60,000).

Sedentariness was assessed by screen time (hours/day spent before TV or computer) and (separately) sitting

time (hours per day spent sitting for any purpose). Incidental exercise was measured by the frequency of

housework or gardening, categorised as follows: ≤3 times per month; 1-2 times per week; 3-4 times per

week; most days. We measured planned physical activity at the beginning and end of the 4-year follow up

period. On both occasions, cohort members reported the number of sessions per week of strenuous and

moderate exercise for at least 20 minutes, and of walking for at least 10 minutes. We derived an “overall

measure” of planned physical activity calculated separately at both the baseline and the 4-year mark. The

measure was weighted as follows: (2 × strenuous + 1 × moderate + 1 × walking) sessions per week. This

weighting system is based on the recommendation of the International Physical Activity Questionnaire and

the Active Australia Survey as used in other analyses of the cohort data [11 12]. Finally, for each individual,

the “overall measures” of weekly exercise for 2005 and 2009 were added and then averaged by dividing by

2, creating a longitudinal measure of planned physical activity (LPPA).

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Smoking status was classified as never, ex-smoker or current-smoker. Alcohol exposure was classified by

four categories: never, ex-drinker, occasional drinker or current-drinker. Body mass index (BMI) was

calculated from self-reported height in metres and weight in kilograms as weight/ height2. It was divided

into 4 categories as follows according to Asian criteria:[8 13-16] underweight (BMI <18.5), normal (18.5 to

<23), overweight (23 to <25), and obese (≥25). Foods that could potentially influence blood pressure (deep

fried, instant, roast or smoked, soybean products and soft drinks) were assessed for consumption frequency

based on a five-point Likert scale ranging from less than once a month to once or more a day. Western-style

fast food exposure was noted on a three-point scale from less than once to more than 3 times per month.

Fruit and vegetable consumption were recorded as standard serves eaten per day.

Statistical analyses

All analyses were performed using SPSS software. The incidence of hypertension and its 95% confidence

interval (CI) were calculated for each value of each categorical variable in both male and female participants

and the influence on incidence by each variable was evaluated by Chi-square test. For statistical inference,

all p-values were 2 tailed and significance was set at 5%.

Relative risks in a large study of an uncommon disease (incidence less than 10%) can be accurately

estimated as odds ratios [17]. Accordingly, for each risk variable, the relative risk (RR) and 95% confidence

interval were estimated using logistic regression to calculate the bivariate odds ratio for hypertension.

Adjusted RRs (ARRs) were estimated by calculating multivariate logistic regression odds ratios. The ARRs

were controlled for confounding by age, marital status, SES, BMI, underlying diseases and personal

behaviours (cigarette smoking and alcohol drinking). A variable was included in a multivariate model if

bivariate analysis had indicated a statistically significant association with incidence of hypertension. Some

variables were included because earlier analyses reported elsewhere had shown significant or substantial

association with hypertension.

Results

Baseline Characteristics

Baseline characteristics of study participants self-reporting as normotensive in 2005 are shown in Table 1.

The highest proportion of males resided in the North-eastern regions and Central while there were more

females in the Central and Bangkok area. More than half of the male and female participants lived in urban

areas. Males had a higher monthly income than females whereas females had a higher educational

attainment than males. The distribution of household assets for males and females was similar and over half

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of them were in medium and high categories. The study population had a similar socio-demography, income

and location of residence to the general Thai population [9].

Incidence and risks of hypertension

Overall, the incidence of self-reported hypertension in Thai adults was 3.5% and the rate in males was more

than twice the corresponding rate in females (5.2% vs. 2.1%) (Table 2). In males and females, the incidence

of hypertension increased with increasing age. Marriage or having a partner increased the risk of

hypertension in females only. Educational attainment and personal income had no influence on the risk of

hypertension in both sexes. In males and females, the risk of hypertension increased with an increased BMI.

The risk of hypertension increased in both males and females who had diabetes mellitus, high blood lipids

and kidney disease.

Planned exercise, averaged across the 4-year follow-up, was protective for males. In males, higher LPPA

(≥15 sessions / week) associated with lower incidence of hypertension however this was not observed in

females.

In males, current-smokers had a higher risk of developing hypertension than non-smokers while in females,


risk of incident hypertension; patterns of relative risks were similar for females but, reflecting the low

frequency of female drinking, did not reach statistical significance. In males, the risk of hypertension had a

direct association with the frequency of instant food consumption but there was no such association detected

in females.

Over the 4-year period, a variety of factors that could have been risks for hypertension were shown not to be

in this setting (data not shown). Thus, in males and females, factors that had no statistically significant

influence on the longitudinal risk of hypertension incidence were urbanization status, non-participation in

housework or gardening, high levels of television and computer watching, sleeping and sitting time, and

food consumption habits that included deep fried food and soft drink, Western fast food, roasted or smoked

foods, fruit, vegetables and soybean products.

Discussion

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This large prospective cohort of adults living all over Thailand has been the first studied nationally for a

wide array of risk factors for incident hypertension. Overall, the 4-year incidence of hypertension from 2005

to 2009 was 3.5%, notably higher in men (5.2%) than women (2.1%). In both sexes, age, obesity and co-

morbidity with diabetes mellitus, high blood lipids and kidney disease strongly linked to hypertension

incidence; in males, instant food consumption, smoking and drinking alcohol had a moderate adverse effect

while planned exercise averaging 15 or more sessions per week over the 4-year period was substantially

protective, reducing risk by 22%. In females, having a partner linked to an increased incidence of

hypertension.

The age effect on hypertension incidence noted by us is consistent with findings of many other population

studies of hypertension including (for example) a longitudinal study in China [18] and cross-sectional

studies in Korea [19], Taiwan [20] and the USA [21]. The noticeably greater incidence of hypertension in

men than in women that we found in Thailand has also been reported from many parts of the world

including neighboring Malaysia [22] and distant USA [23] as well as in a recent global review [24].

In men and women of the Thai cohort, a progressively higher BMI was positively and significantly

associated with an increased risk of incident hypertension over the four years. This finding was similar to

that reported for other prospective cohorts in the US [25 26] and Finland [27]. Furthermore, after seven

years of follow-up in a US study [28], weight loss associated with a decreased risk of incident hypertension.

Among a cohort of US nurses, the risk of incident hypertension increased 5% for each kilogram addition of

weight [29], and rose 15% for each increase of one kilogram per meter squared of BMI in Taiwan [18].

These results suggest that the adverse effect of high BMI on risk of hypertension does not depend on

ethinicity or sex and is wide spread.

In our cohort, we noted a higher risk of incident hypertension among those with diabetes mellitus. This

finding is consistent with longitudinal studies in the USA [30 31] which reported, respectively, that in

diabetic patients the risk of incident hypertension rose 41% and 56%. As well, prospective cohort studies in

Japan showed that diabetes [32] and impaired fasting blood glucose [33] were associated with an increased

risk of hypertension incidence. Supportive cross-sectional results emerge from studies in diverse settings

including Bangladesh and India [34], Barbados [35] and the USA [36]. A causal association between

diabetes and hypertension is suspected and possible mechanisms include endothelial dysfunction and

vascular inflammation [37].

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We also found that high blood lipids significantly associated with increased risk of incident hypertension.

This supports the results from previous longitudinal studies in men [38 39], women [40 41] and adults [32

42]. The risk of hypertension increased with an increase of total cholesterol, triglyceride and low-density

lipoprotein cholesterol levels and decreased with an increase of high-density lipoprotein cholesterol level

[38 39 41].The mechanism by which dyslipidemia provokes high blood pressure is uncertain but could

reflect blood vessel dysfunction and damaged endothelium [43].

Among men and women in the Thai cohort, kidney disease strongly associated with increased risk of

hypertension incidence. This result is supported by cross-sectional data from the Czech Republic [44] and

the USA [45]. Microalbuminuria is a biomarker for renal hypertension [45] and the risk increases with the

severity of kidney impairment, revealed by the serum creatinine level [46 47]. Glomerular damage is more

closely connected with hypertension than tubular or interstitial disease [47]. Chronic kidney disease

facilitates high blood pressure through many mechanisms including excessive intravascular volume,

increased endothelin production, activity of the renin-angiotensin system and sympathetic nervous system

and decreased vasodilators, nitric oxide production and endothelial function [48].

In men we found that cigarette smoking modestly associated with increased risk of developing hypertension.

This is consistent with many other reports such as longitudinal studies in Japanese [49] and American men

[50] and a cross-sectional study in French men [51]. In addition, smoking Jordanian men had significantly

higher blood pressure than their non-smoking counterparts [52]. However, we also found that smoking had

no influence on hypertension in women. This result for females is compatible with reports from Korea [53]

and the USA [54]. In contrast, one prospective US study [55] reported an increased risk of hypertension

among women. It is likely that men tend to smoke more cigarette than women and the impact of smoking on

hypertension is a dose-response pattern [49].

Regular alcohol consumption was strongly associated with an increased risk of incident hypertension. This

result is supported by findings from longitudinal studies in Japan [56 57] and cross-section studies in

China[58] and Korea [53]. In Japanese men, alcohol consumption, particularly more than 200 grams per

week, significantly associated with an increase of blood pressure [59] while alcohol restriction was

noticeably related to a decreased blood pressure [60]. Among our Thai cohort females, alcohol consumption

had no influence on hypertension; this result was supported by longitudinal data from Japan [56] and cross-

sectional data from Korea [53]. In American females the quantity of alcohol consumption per week had no

effect on systolic blood pressure [61]. Males usually consume more alcohol than females and the

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hypertension risk is linear with a dose-response [57 62]. Our results suggest that regular alcohol

consumption, especially in males, is a significant risk factor for developing hypertension.

Marital status in males had no influence on hypertension which supports the results from more economically

developed countries, the USA and Korea [53 54]. However, in middle-income countries, results diverged:

married males, when compared to their unmarried counterparts, had a higher risk of hypertension in

Barbados [35] and a lower risk in Poland [63]. Married individuals had higher emotional and social support

and lower stress [63] and probability of being a current smoker [64]. We found incident hypertension was

relatively more frequent among married females, unlike the no-sex-link pattern in developed countries such

as the USA and Korea [53 54]. The influence of marrital status on hypertension varies from one country to

another country partly due to the difference of socio-economy and social structure. For our Thai cohort, the

pattern in males was similar to that in developed countries and in females it was not.

Participant educational attainment did not protect against hypertension in either sex. This is similar to cross-

sectional results for adults in developed countries such as Korea [53] and the USA [36 65]. However, other

studies in various settings and with diverse designs reported educational attainment protects against

hypertension in adults; these included a prospective cohort in middle income Thailand [5], a cross-sectional

study in middle income Malaysia [22] and a cross-sectional study in high income USA [66]. Opposite

findings have been reported in low income settings in both Bangladesh and India [34] where education was

a risk factor for hypertension. Taken collectively, these data suggest that income modifies the protective

education-hypertension effect, inverting it when income is low and boosting it when income is high. Our

middle-income cohort could be in the middle stage of this education effect as it is transiting from the low-

income pattern.

We found no association of personal monthly income and risk of hypertension in either sex. This was similar

to previous studies in middle-income countries including a longitudinal study in Thailand [5] and a cross-

sectional study in Malaysia [67] and in cross-sectional studies in high-income countries such as in Korea

[53] and the USA [21 36]. However, income had an inverse association with risk of hypertension in another

study in high-income developed countries such as the USA [65] while it had a direct association in a low-

income developing country such as Ghana [68]. The health transition in Thailand is likely to be in the

middle stage, according to the concept of a tipping-point for the relationship between socio-economic status,

body size and hypertension risk factors. High income, large body size and high blood pressure is seen in

developing countries while in developed countries, high income is a protective factor [69-71]. Indeed, the

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Thai cohort has already been shown to be at a transitional point for metabolic states because females had an

inverse relationship between income and BMI whereas males had a positive (traditional) relationship [14].

However, now all Thais benefit from universal health insurance so access to health care is not dependent on

their income making disease associations more attenuated than before [72].

In our cohort, the reduction of risk of hypertension incidence in males but not in females by a longitudinal

measure of planned physical activity was comparable with a prospective study in the middle-aged American

whites [73]. In another prospective study in middle-aged Finns, the hypertension protective effect of

vigorous physical activity or total energy expenditure from leisure-time physical activity was observed in

men but not in women [74]. Such physical activity among females may be less intense than among males so

having no effect on the risk of hypertension [74]. A large Finnish study [27] demonstrated that the incidence

of hypertension was inversely associated with the level of physical activity in a dose-response manner in

both sexes. In our cohort study, risk of obesity had an inverse association with quantified planned exercise in

both sexes but the effect was significantly stronger in males than in females [12]. As Thailand progresses

economically, more people migrate to urban areas and decrease their physical activity [7]. Therefore, in the

future, Thai people may encounter a higher risk of hypertension due to a lower physical activity.

Instant food - mostly combinations of carbohydrate, fat and salt - associated with an increased risk of

incident hypertension in males but not in females. Other foods, fruit and vegetables had no impact on

hypertension. This may be as a result of men comsuming more instant foods, such as instant noodles, than

women. For example a study in Korea showed daily instant food consumption in men and women averages

23.7 and 11.1 grams respectively [75]. Other studies showed that carbohydrate [76 77], fruit and vegetables

[78 79] consumption had no influence on hypertension. Most students consume instant noodles which lead

to a higher intake of energy, fat, sodium, thiamine, and riboflavin but a lower intake of protein, calcium,

phosphorus [75]. Koreans who favor instant noodles have a salt intake more than three times higher than the

daily recommendation (6.4 vs 2 gms) [75]. Daily salt consumption of Thai people has been reported to

average 10.8gm which is much higher than the recommendation

(http://www.worldactiononsalt.com/worldaction/asia/75286.pdf). High salt consumption was associated with

an increased risk of developing hypertension in a longitudinal study in Taiwan [80] and in cross-sectional

studies in China [81 82] while other reports revealed that salt restriction reduced blood pressure [83 84].

High plasma sodium, due to an overwhelmed capacity of the kidney to excrete excessive salt consumption,

leads to excessive intravascular volume and high blood pressure [85]. It seems reasonable to conclude that

high salt intake from instant noodle consumption is likely to be causally associated with an increased risk of

hypertension in Thailand.

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factors on hypertension development. Indeed, the study size along with its national representation are

important factors to consider when exploring study validity. The influence of risk factors on hypertension

incidence is clearly demonstrated since this is a large longitudinal cohort covering a 4-year period. As a

consequence, the independent risk factors for hypertension in Thais can be identified. Our cohort represents

Thais well in geography and socio-economy [9] so the results reflect the trend of health-risk transition in the

Thai population. Because of the better education attainment of STOU students combined with their

representative income and geographical location, they represent the next generation of Thais. It would be

reasonable to conclude that our 4-year follow-up results show the future hypertension trends for Thai people.


But a study of the validity of self-reported weight and height in our cohort found that the accurary was quite

acceptable [86]. As well, we have conducted a validation study of self-reported hypertension (Prasutr

Thawornchaisit, 2013, under review) in a random age-sex matched sub-sample of the cohort reporting

hypertension (n=240) or no hypertension (n=240). We found the sensitivity was high (82%) and that

negative reports were usually accurate (86%). The findings from our study are likely to be robust and

represent well the future trends of health-risk transition in middle-income Thailand and similar ASEAN

countries.

In conclusion, older age, obesity and underlying morbidity due to diabetes, high blood lipids and kidney

disease were strongly associated with an increased risk of incident hypertension in both sexes while in

males, physical inactivity, instant food consumption, smoking and drinking alcohol had a moderate

association. Sedentary life-style and the consumption of friut and vegetables had no detected influence on

hypertension. The Thai health-risk transition is likely to be in the middle stage since education attainment

and income still have no net effect to protect against hypertension. Prevention should focus on obesity, high

blood lipids and high salt consumption and people should be encouraged to increase physical exercise and

consume low fat foods and less instant foods. A reduction of salt consumption should be a national policy by

limiting the concentration of salt in ready-to-eat and industrial foods. Smoking and drinking cessation

should be promoted for males. Thailand should also consciously aim to take advantage of its culturally

determined low rate of drinking and smoking among women and ensure that there is no attempt to

undermine this situation and develop the market for the female half of the population.

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Thai Cohort Study Team*

Thailand: Jaruwan Chokhanapitak, Suttanit Hounthasarn, Suwanee Khamman, Daoruang Pandee, Suttinan

Pangsap, Tippawan Prapamontol, Janya Puengson, Sam-ang Seubsman, Boonchai Somboonsook, Nintita

Sripaiboonkij, Pathumvadee Somsamai, Prasutr Thawornchaisit, Duangkae Vilainerun, Wanee

Wimonwattanaphan, Cha-aim Pachanee, Arunrat Tangmunkongvorakul, Benjawan Tawatsupa, Wimalin

Rimpeekool.

Australia: Chris Bain, Emily Banks, Cathy Banwell, Bruce Caldwell, Gordon Carmichael, Tarie Dellora,

Jane Dixon, Sharon Friel, David Harley, Matthew Kelly, Tord Kjellstrom, Lynette Lim, Anthony

McMichael, Tanya Mark, Adrian Sleigh, Lyndall Strazdins, Vasoontara Yiengprugsawan, Susan Jordan,

Janneke Berecki-Gisolf, Rod McClure.

Acknowledgements and Funding

This study was supported by the International Collaborative Research Grants Scheme with joint grants from

the Wellcome Trust UK (GR071587MA) and the Australian National Health and Medical Research Council

(268055), and by a global health grant from the NHMRC (585426). We thank the staff at Sukhothai

Thammathirat Open University (STOU) who assisted with student contact and the STOU students who are

participating in the cohort study. We also thank Dr Bandit Thinkamrop and his team from Khon Kaen

University for guiding us successfully through the complex data processing.

Conflict of interest

The authors declare that there are no conflicts of interest.

Ethical considerations

Ethical approval was obtained from Sukhothai Thammathirat Open University Research and Development

Institute (protocol 0522/10) and the Australian National University Human Research Ethics Committee

(protocol 2004344 and 2009570). Informed, written consent was obtained from all participants.

Authors' contributions

PT, FD, CR, SS, and AS jointly planned the study. PT performed the data collection and analysis and

drafted the manuscript. SS managed and coordinated the data collection. FD, CR, SS and AS participated in

the study conduction and manuscript preparation. FD, CR, SS and AS commented and corrected the

manuscript. All authors read and approved the final manuscript.

Data Sharing

No additional data available.

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Table 1 Characteristics of 57558 participants normotensive at the 2005 Thai Cohort Study baseline

Male Female Difference Factor n % n % P-valuea

Demographic data

Participants 25320 44.0 32238 56.0 <0.0001 Age (y) mean 32.9 30.0 <0.0001

b

(SD) (8.5) (7.6) Age group <0.0001 ≤30 y 11293 44.6 19229 59.6 31-40 y 9177 36.2 9638 29.9 >40 y 4850 19.2 3371 10.5 Married/partnered <0.0001 No 11060 44.8 18851 60.1 Yes 13607 55.2 12513 39.9 Regions <0.0001 Bangkok 3488 13.9 6057 18.9 Central 5712 22.7 8267 25.8 North 5180 20.6 5818 18.1 North-east 6142 24.4 5760 18.0 East 1515 6.0 1922 6.0 South 3103 12.3 4254 13.3 Urbanization status

c <0.0001

Rural–rural (RR) 11512 46,1 13895 43.6 Rural–urban (RU) 7891 31.6 9546 29.9 Urban–rural (UR) 1078 4.3 1344 4.2 Urban–urban (UU) 4495 18.0 7114 22.3

Socioeconomic status

Education level <0.0001 High school 13366 52.9 13135 40.8 Diploma 5749 22.8 9791 30.4 University 6153 24.4 9231 28.7 Personal monthly income (baht)

d <0.0001 ≤7000 8025 32.3 13890 44.1 7001–10000 5790 23.3 7578 24.0 10001–20000 7549 30.4 7194 22.8 >20000 3452 13.9 2851 9.0 Household assets

e (baht)

d <0.001

Low 9852 39.1 12434 38.7 Medium 8065 32.0 9863 30.7 High 7298 28.9 9804 30.5 aChi-square test b unpaired t test cLocation of residence (rural, R, or urban, U) at age 10-12 years and again in 2005. dAt the time of the survey in 2009, US$1 = 31 Thai baht eReplacement value in Thai baht: low ≤30,000, medium 30,001-60,000 and high >60,000

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Table 2 Hypertension incidence and association with risk factors in male and female participants.

Males Females HT(n) Incia%(95% CI) ARRb(95% CI) HT(n) Incia%(95% CI) ARRb(95% CI) Participants 1306 5.2 (4.9-5.4) 690 2.1 (2.0-2.3)

Demography

Age group

≤30 y 279 2.5 (2.2-2.8) 1 215 1.1 (0.97-1.3) 1 31-40 y 484 5.3 (4.8-5.7) 1.66 (1.39-1.98) 245 2.5 (2.23-2.9) 1.93 (1.56-2.39) >40 y 543 11.2 (10.3-12.1) 3.13 (2.57-3.81) 230 6.8 (6.0-7.7) 4.2 (3.26-5.42) P-trend <0.0001 <0.0001 <0.0001 <0.0001

Marital status (married/partnered)

No 368 3.3 (3.0-3.7) 1 303 1.6 (1.43-1.8) 1 Yes 896 6.6 (6.17-7.0) 0.97 (0.83-1.12) 368 2.9 (2.65-3.2) 1.22 (1.03-1.45)

Socio-economic status

Education level

High school 697 5.2 (4.8-5.6) 1 303 2.3 (2.05-2.57) 1 Diploma 276 4.8 (4.25-5.4) 1.0 (0.86-1.17) 180 1.8 (1.57-2.1) 0.81 (0.66-0.99) University 331 5.4 (4.8-5.9) 0.93 (0.8-1.1) 204 2.2 (1.9-2.51) 0.87 (0.71-1.07) P-trend 0.83 0.61 0.463 0.1 Personal monthly income (baht)c ≤7000 268 3.3 (2.95-3.7) 1 217 1.6 (1.36-1.8) 1 7001-10000 229 4.0 (3.45-4.5) 1.0 (0.81-1.2) 142 1.9 (1.57-2.2) 1.1 (0.87-1.37) 10001-20000 497 6.6 (6.0-7.14) 1.1 (0.91-1.31) 196 2.7 (2.35-3.1) 0.97 (0.77-1.23) >20000 289 8.4 (7.46-9.3) 1.0 (0.8-1.25) 122 4.3 (3.54-5.0) 1.04 (0.78-1.39) P-trend <0.0001 0.527 <0.0001 0.783

BMI classificationd

Underweight 359 2.9 (2.62-3.2) 0.46 (0.27-0.78) 60 0.85 (0.63-1.15) 0.9 (0.67-1.21) (BMI <18.5) Normal 16 1.1 (0.56-1.6) 1 258 1.4 (1.2-1.5) 1 (18.5 ≤ BMI < 23) Overweight 333 5.9 (5.3-6.54) 1.66 (1.41-1.95) 129 3.9 (3.3-4.62) 2.32 (1.8-2.91) (23 ≤ BMI < 25) Obese 575 10.4 (9.6-11.2) 2.82 (2.43-3.27) 231 7.4 (6.4-8.27) 4.14 (3.4-5.05) (BMI ≥25) P-trend <0.0001 <0.0001 <0.0001 <0.0001

aIncidence of Hypertension

bAdjusted relative risks (ARR) were calculated from multi-variate logistic regression models of hypertension

adjusted for age, marital status, education, income, BMI category, underlying diseases, personal behaviours. cAt the time of the survey in 2005, US$1 = 42 Thai baht dAsian standard BMI classification

Continued….

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Table 2 (continued...)

Males Females HT(n) Inci

a%(95% CI) ARR

b(95% CI) HT(n) Inci

a%(95% CI) ARR

b(95% CI)

Physical activities

Weighted total sessions exercise-related physical activity (average between 2005 and 2009) 0-7 ses/wc 198 6.3 (5.5-7.1) 1 162 2.2 (1.8-2.6) 1 8-14 ses/w 589 5.2 (4.8-5.6) 0.9 (0.76-1.07) 352 2.1 (1.9-2.3) 1.0 (0.82-1.23)

≥15 ses/w 380 4.4 (4.0-5.0) 0.78 (0.65-0.95) 119 2.2 (1.8-2.6) 1.0 (0.77-1.3)

P-trend <0.0001 <0.029 0.905 1.0

Underlying diseases

Diabetes mellitus

No 1251 5.0 (4.7-5.27) 1 674 2.1 (1.9-2.26) 1 Yes 55 18.3 (13.9-22.7) 1.81 (1.29-2.52) 16 10.7 (5.7-15.8) 2.54 (1.41-4.56)

High lipids

No 983 4.4 (4.13-4.67) 1 576 1.9 (1.76-2.1) 1 Yes 323 10.8 (9.7-11.9) 1.4 (1.21-1.63) 114 5.4 (4.47-6.4) 1.38 (1.09-1.75)

Kidney diseases

No 1248 5.1 (4.8-5.33) 1 659 2.1 (1.9-2.26) 1 Yes 58 9.6 (7.2-11.9) 1.62 (1.19-2.2) 31 3.9 (2.52-5.2) 1.77 (1.19-2.63)

Personal behaviours

Smoking status Never 506 4.1 (3.7-4.4) 1 617 2.1 (1.9-2.23) 1 Ex-smoker 496 6.6 (6.0-7.13) 1.15 (1.0-1.32) 37 3.2 (2.2-4.22) 1.28 (0.88-1.87) Cur-smokerd 276 5.8 (5.16-6.5) 1.22 (1.04-1.44) 8 3.1 (0.97-5.2) 1.54 (0.74-3.2) P-trend <0.0001 <0.032 <0.008 0.23

Drinking status

Never 105 3.9 (3.2-4.7) 1 268 2.1 (1.8-2.32) 1 Ex-drinker 155 5.7 (4.85-6.6) 0.98 (0.74-1.3) 50 2.2 (1.6-2.85) 1.14 (0.82-1.59) Occ- drinkere 821 4.8 (4.45-5.1) 1.0 (0.8-1.25) 352 2.1 (1.9-2.36) 1.14 (0.96-1.36) Reg- drinker

f 212 8.6 (7.5-9.7) 1.61 (1.23-2.11) 9 4.7 (1.66-7.7) 1.83 (0.86-3.9)

P-trend <0.0001 <0.0001 0.471 0.254

Food consumption habit

Instant food

<1 time/m 335 6.3 (5.6-6.95) 1 168 2.8(2.36-3.2) 1 1-3 times/m 485 5.1 (4.63-5.5) 1.02 (0.87-1.19) 273 2.1 (1.84-2.3) 0.95 (0.77-1.17) 1-2 times/wk 280 4.4 (3.9-4.9) 1.09 (0.91-1.30) 153 1.9 (1.6-2.2) 1.04 (0.81-1.33) 3-6 times/wk 165 5.0 (4.3-5.75) 1.36 (1.1-1.69) 73 1.8 (1.4-2.22) 1.14 (0.84-1.55) ≥1 times/d 32 5.5 (3.6-7.33) 1.67 (1.11-2.52) 18 2.3 (1.3-3.35) 1.48 (0.86-2.53) P-trend <0.002 <0.008 <0.002 0.403 aIncidence of Hypertension

bAdjusted relative risks were calculated from multi-variate logistic regression models of hypertension adjusted for age, marital status, education, income, BMI category, underlying diseases, personal behaviours. cSessions / week dCurrent-smoker eOccasional drinker fRegular drinker

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84. Sacks FM, Svetkey LP, Vollmer WM, et al. Effects on blood pressure of reduced dietary sodium and the Dietary

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STROBE 2007 (v4) Statement—Checklist of items that should be included in reports of cohort studies

Section/Topic Item

# Recommendation Reported on page #

Title and abstract 1 (a) Indicate the study’s design with a commonly used term in the title or the abstract 1

(b) Provide in the abstract an informative and balanced summary of what was done and what was found 2

Introduction

Background/rationale 2 Explain the scientific background and rationale for the investigation being reported 3

Objectives 3 State specific objectives, including any prespecified hypotheses 3

Methods

Study design 4 Present key elements of study design early in the paper 3

Setting 5 Describe the setting, locations, and relevant dates, including periods of recruitment, exposure, follow-up, and data

collection

4

Participants 6 (a) Give the eligibility criteria, and the sources and methods of selection of participants. Describe methods of follow-up 3

(b) For matched studies, give matching criteria and number of exposed and unexposed 3-4

Variables 7 Clearly define all outcomes, exposures, predictors, potential confounders, and effect modifiers. Give diagnostic criteria, if

applicable

4

Data sources/

measurement

8* For each variable of interest, give sources of data and details of methods of assessment (measurement). Describe

comparability of assessment methods if there is more than one group

4-5

Bias 9 Describe any efforts to address potential sources of bias 11

Study size 10 Explain how the study size was arrived at 3

Quantitative variables 11 Explain how quantitative variables were handled in the analyses. If applicable, describe which groupings were chosen and

why

4-5

Statistical methods 12 (a) Describe all statistical methods, including those used to control for confounding 5

(b) Describe any methods used to examine subgroups and interactions 5

(c) Explain how missing data were addressed 5

(d) If applicable, explain how loss to follow-up was addressed 5

(e) Describe any sensitivity analyses 5

Results 5-6

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Participants 13* (a) Report numbers of individuals at each stage of study—eg numbers potentially eligible, examined for eligibility, confirmed

eligible, included in the study, completing follow-up, and analysed

3

(b) Give reasons for non-participation at each stage 4

(c) Consider use of a flow diagram

Descriptive data 14* (a) Give characteristics of study participants (eg demographic, clinical, social) and information on exposures and potential

confounders

5

(b) Indicate number of participants with missing data for each variable of interest

(c) Summarise follow-up time (eg, average and total amount) 4

Outcome data 15* Report numbers of outcome events or summary measures over time 6

Main results 16 (a) Give unadjusted estimates and, if applicable, confounder-adjusted estimates and their precision (eg, 95% confidence

interval). Make clear which confounders were adjusted for and why they were included

6

(b) Report category boundaries when continuous variables were categorized 6

(c) If relevant, consider translating estimates of relative risk into absolute risk for a meaningful time period 6

Other analyses 17 Report other analyses done—eg analyses of subgroups and interactions, and sensitivity analyses 6

Discussion

Key results 18 Summarise key results with reference to study objectives 7

Limitations

Interpretation 20 Give a cautious overall interpretation of results considering objectives, limitations, multiplicity of analyses, results from

similar studies, and other relevant evidence

11

Generalisability 21 Discuss the generalisability (external validity) of the study results 11

Other information

Funding 22 Give the source of funding and the role of the funders for the present study and, if applicable, for the original study on

which the present article is based

12

*Give information separately for cases and controls in case-control studies and, if applicable, for exposed and unexposed groups in cohort and cross-sectional studies.

Note: An Explanation and Elaboration article discusses each checklist item and gives methodological background and published examples of transparent reporting. The STROBE

checklist is best used in conjunction with this article (freely available on the Web sites of PLoS Medicine at http://www.plosmedicine.org/, Annals of Internal Medicine at

http://www.annals.org/, and Epidemiology at http://www.epidem.com/). Information on the STROBE Initiative is available at www.strobe-statement.org.

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Journal: BMJ Open

Manuscript ID: bmjopen-2013-002826.R1


Date Submitted by the Author: 10-Apr-2013




Epidemiology

Secondary Subject Heading: Epidemiology, Public health



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Health-risk factors and the incidence of hypertension: 4-year prospective

findings from a national cohort of 60,569 Thai open university students





Telephone: 662-585-8015

Fax: 662-912-0121








*Thailand: Jaruwan Chokhanapitak, Suttanit Hounthasarn, Suwanee Khamman, Daoruang Pandee, Suttinan




Rimpeekool.





Running Head: Health-risks and hypertension incidence in the Thai Cohort Study

Key words: hypertension; health-risks; cohort; Thailand; socioeconomic

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Abstract

Objective

This study evaluates the impact of a number of demographic, biological, behavioural and lifestyle health-

risk factors on the incidence of hypertension in Thailand over a 4-year period.

Design

A 4-year prospective study of health-risk factors and their effects on incidence of hypertension in a national

Thai Cohort Study (TCS) from 2005 to 2009

Setting


(particularly cardiovascular disease) have emerged as major health issues. Hypertension is a major risk

factor for heart attack and stroke and cross-sectional studies have indicated that the prevalence is increasing.

Study participants

Sukhothai Thammathirat Open University students (57,558) who participated in both 2005 and 2009

questionnaire surveys and who were normotensive in 2005 were included in the analysis.

Measures

Adjusted relative risks associating each risk factor and incidence of hypertension by sex, after controlling for

confounders such as age, socio-economic status, body mass index (BMI) and underlying diseases.

Results


that in women (5.2% vs. 2.1%). In both sexes, hypertension associated with age, higher BMI and co-

morbidities but did not associate with income and education. In men, hypertension associated with physical

inactivity, smoking, alcohol and fast food intake. In women, hypertension was related to having a partner.

Conclusion

In both men and women, hypertension strongly associated with age, obesity and co-morbidities while it had

no association with socio-economic factors. The cohort pattern of socio-economy and hypertension reflects

that the health-risk transition in Thais is likely to be at the middle stage. Diet and lifestyle factors associate

with incidence of hypertension in Thais and may be amenable targets for hypertension control programs.

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Article summary

Article focus

In a large Thai Cohort Study, we measured the effect of exposure to health-risk factors recorded in 2005 on

the incidence rate of hypertension over the following 4 years. This is part of a study of the health-risk

transition underway in Thailand. We investigated socio-demographic factors, co-morbidity, body size,

physical activity and health behaviour. Cohort members are Open University students, live nationwide, are

well educated and of modest means, representing the next generation of adult Thais.

Key Messages

Overall, the incidence of self-reported hypertension in Thai adults was 3.5% with the rate for males much

higher than females (5.2% vs. 2.1%). In both sexes hypertension incidence was associated with age, higher

body mass index, kidney disease, diabetes and high lipids, but not with socioeconomic status.

Marriage or partnering increased risk of hypertension in females but not in males. Planned physical activity,

averaged across the 4-year follow-up, protected males: ≥15 sessions /week associated with lower incidence

of hypertension. However, this was not observed in females.

In males, current-smokers had a higher risk of developing hypertension than non-smokers while in females


risk of incident hypertension.

Strengths

In Thailand, this cohort constitutes the largest longitudinal study of health-risk factors and hypertension

development. As a consequence, many independent risk factors for hypertension in Thais can be identified.

Our cohort represents Thais well in geography and socio-economy so the results reflect trends of the health-

risk transition in the population.

Limitations

Our study relies on self-report. There may be recall and reporting errors. Some risk factors may take more

than four years to produce hypertension and will manifest as the cohort ages.

Introduction

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2004 [4-6]. The recent Thai National Health Examination Survey (NHES) in 2009 reported the prevalence

of hypertension in adults was 21.5% [4]. The emergence of hypertension has been the result of rapid

socioeconomic development which has resulted in one third of Thais migrating to urban areas [7].

Urbanization has been associated with increased obesity as people become less physically active and adopt

sedentary life styles such as spending more time watching television, sitting and using computers [7 8].

These factors, in association with Thailand’s ageing population [9], underpin the importance of controlling

hypertension in Thai community.

There is limited longitudinal research on health risk factors and hypertension incidence in Thailand [5]. The

purpose of this study is to address that knowledge gap. We prospectively examined the influence of an array

of demographic, biological, health-risk and lifestyle factors on the incidence of hypertension during 4 years

of follow-up in the Thai Cohort Study (TCS). This is part of an overarching research program investigating

Thailand’s health-risk transition from high maternal-child and infectious disease mortality to increased

longevity and emerging chronic disease. The large national cohort of Thai adults reported on here has been

followed since 2005 for risk factor trends and associated disease outcomes, including hypertension.

Methods

Study population




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Incident hypertension was defined as being normotensive in 2005 and self-reported doctor diagnosed

hypertensive in 2009. Hypertension incidence was the dependent variable for analyses and the person-time

denominator included all individuals at risk - those 57,558 participants with longitudinal data who were

negative for hypertension in 2005, the beginning of the 4-year study period.

Risk Factors

Hypertension was defined as describe above, underlying diseases diagnosed by a doctor were also reported

including diabetes mellitus, kidney diseases and high blood lipids, all of which were investigated as

potential risk factors of hypertension.

















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calculated from self-reported height in metres and weight in kilograms as weight/height2. It was divided into

4 categories as follows according to Asian criteria:[8 13-16] underweight (BMI <18.5), normal (18.5 to




















Results





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Overall, the incidence of self-reported doctor diagnosed hypertension in Thai adults was 3.5% and the rate in

males was more than twice the corresponding rate in females (5.2% vs. 2.1%) (Table 2). In males and

females, the incidence of hypertension increased with increasing age. Marriage or having a partner increased

the risk of hypertension in females. Educational attainment and personal income had no influence on the risk

of hypertension in both sexes. In males and females, the risk of hypertension increased with an increased

BMI. The risk of hypertension increased in both males and females who had diabetes mellitus, high blood

lipids and kidney disease.

Planned physical activity, averaged across the 4-year follow-up, was protective for males. In males, higher

LPPA (≥15 sessions / week) associated with lower incidence of hypertension; however, this association was

not observed in females. In males, current-smokers had a higher risk of developing hypertension than non-

smokers while in females, smoking (which was rare) had no apparent hypertension effect. Among males,

regular drinking increased the risk of incident hypertension; patterns of relative risks were similar for

females but, reflecting the low frequency of female drinking, did not reach statistical significance. In males,

the risk of hypertension had a direct association with the frequency of instant food consumption but there

was no such association detected in females.

Over the 4-year period, a variety of factors that could have been risks for hypertension over a longer period

were found not to be in this setting (data not shown). Thus, in males and females, factors that had no

statistically significant influence on the longitudinal 4-year risk of hypertension incidence were urbanization

status, sedentary lifestyle (non-participation in housework or gardening, high levels of television and

computer watching, sleeping and sitting time), and food consumption habits that included deep fried food

and soft drink, Western fast food, roasted or smoked foods, fruit, vegetables and soybean products.

Discussion

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to 2009 was 3.5%, notably higher in men (5.2%) than women (2.1%). These incidence rates are drawn from

a cohort of adults on average younger than the Thai population so they are lower than corresponding rates of

the adult population. However, our focus was on risk factor associations and we noted that in both sexes,

age, obesity and co-morbidity with diabetes mellitus, high blood lipids and kidney disease strongly linked to

hypertension incidence. In males, instant food consumption, smoking and drinking alcohol had a moderate

adverse effect on hypertension risk while planned physical activity averaging 15 or more sessions per week

over the 4-year period was substantially protective, reducing risk by 22%. In females, having a partner was

associated with increased incidence of hypertension.













ethinicity or sex and is wide spread around the world.







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among women. It is likely that men tend to smoke more cigarettes than women and the impact of smoking

on hypertension is a dose-response pattern [49].


result is supported by findings from longitudinal studies in Japan [56 57] and cross-sectional studies in

China [58] and Korea [53]. In Japanese men, alcohol consumption, particularly more than 200 grams per


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another partly due to the difference of socio-economy and social structure. For our Thai cohort, the pattern

in males was similar to that in developed countries and in females it was not.










income pattern.





study in high-income developed USA [65] while it had a direct positive association in a low-income

developing country such as Ghana [68]. The health transition in Thailand is likely to be in the middle stage,

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according to the concept of a tipping-point for the relationship between socio-economic status, body size and

hypertension risk factors. High income, large body size and high blood pressure is seen in developing

countries while in developed countries, high income is a protective factor [69-71]. Indeed, the Thai cohort

has already been shown to be at a transitional point for metabolic states because females had an inverse

relationship between income and BMI whereas males had a positive (traditional) relationship [14]. However,

now all Thais benefit from universal health insurance so access to health care is not dependent on their

income making disease associations more attenuated than before [72].


measure of planned physical activity was comparable with a prospective study in middle-aged American









future, Thai people may encounter a higher risk of hypertension due to lower physical activity.








phosphorus [75]. Koreans favoring instant noodles have a salt intake more than three times higher than the

daily recommendation (6.4 vs 2 gms) [75]. Daily salt intake of Thai people has been reported to average

10.8gm, much higher than recommended (http://www.worldactiononsalt.com/worldaction/asia/75286.pdf).

High salt consumption was associated with an increased risk of developing hypertension in a longitudinal

study in Taiwan [80] and in cross-sectional studies in China [81 82] while other reports revealed that salt

restriction reduced blood pressure [83 84]. High plasma sodium, due to an overwhelmed capacity of the

kidney to excrete excessive salt consumption, leads to excessive intravascular volume and high blood

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pressure [85]. It seems reasonable to conclude that high salt intake from instant noodle consumption is likely

to be causally associated with an increased risk of hypertension in Thailand.



important factors to consider when exploring study validity and utility. The influence of risk factors on

hypertension incidence is clearly demonstrated since this is a large longitudinal cohort covering a 4-year

period. As a consequence, independent risk factors for hypertension in Thais can be identified. Our cohort

represents Thais well in geography and socio-economy [9] so the results reflect the trend of health-risk

transition in the Thai population. STOU students, with better education attainment combined with their

representative incomes and geographical location, represent the next generation of Thais. It would be



But a study of the validity of self-reported weight and height in our cohort found that the accuracy was quite




negative reports were usually accurate (86%). In another report, we investigated the impact of the non-

responses to the 2009 follow up and found small effects with under-representation of young urban males;

this missing group would have a minor influence on our results and would not be expected to have a high

rate of incident hypertension [87]. The findings from our study are likely to be robust and represent well the

future trends of health-risk transition in middle-income Thailand and similar ASEAN countries.










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Author contribution: PT devised the hypertension study, analysed the data and wrote the paper. FDL and

CR assisted with planning the study, analysis and interpretation. AS and SS conceived and developed the

cohort, and helped plan, analyse and interpret this study. All authors approved the final manuscript.

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Male Female Difference

Factor

n % n % P-valuea

Demographic data


b


c <0.0001





e (baht)

d <0.001

Low 9852 39.1 12434 38.7 Medium 8065 32.0 9863 30.7 High 7298 28.9 9804 30.5 aChi-square test

b unpaired t test cLocation of residence (rural, R, or urban, U) at age 10-12 years and again in 2005. dAt the time of the survey in 2009, US$1 = 31 Thai baht eReplacement value in Thai baht: low ≤30,000, medium 30,001-60,000 and high >60,000

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Males Females

HT(n) Incia%(95% CI) ARR


a%(95% CI) ARR

b(95% CI)

Participants 1306 5.2 (4.9-5.4) 690 2.1 (2.0-2.3)

Demography

Age group

≤30 y 279 2.5 (2.2-2.8) 1 215 1.1 (0.97-1.3) 1 31-40 y 484 5.3 (4.8-5.7) 1.66 (1.39-1.98) 245 2.5 (2.23-2.9) 1.93 (1.56-2.39) >40 y 543 11.2 (10.3-12.1) 3.13 (2.57-3.81) 230 6.8 (6.0-7.7) 4.2 (3.26-5.42) P-trend <0.0001 <0.0001 <0.0001 <0.0001


No 368 3.3 (3.0-3.7) 1 303 1.6 (1.43-1.8) 1 Yes 896 6.6 (6.17-7.0) 0.97 (0.83-1.12) 368 2.9 (2.65-3.2) 1.22 (1.03-1.45)


Education level

High school 697 5.2 (4.8-5.6) 1 303 2.3 (2.05-2.57) 1 Diploma 276 4.8 (4.25-5.4) 1.0 (0.86-1.17) 180 1.8 (1.57-2.1) 0.81 (0.66-0.99) University 331 5.4 (4.8-5.9) 0.93 (0.8-1.1) 204 2.2 (1.9-2.51) 0.87 (0.71-1.07) P-trend 0.83 0.61 0.463 0.1 Personal monthly income (baht)c ≤7000 268 3.3 (2.95-3.7) 1 217 1.6 (1.36-1.8) 1 7001-10000 229 4.0 (3.45-4.5) 1.0 (0.81-1.2) 142 1.9 (1.57-2.2) 1.1 (0.87-1.37) 10001-20000 497 6.6 (6.0-7.14) 1.1 (0.91-1.31) 196 2.7 (2.35-3.1) 0.97 (0.77-1.23) >20000 289 8.4 (7.46-9.3) 1.0 (0.8-1.25) 122 4.3 (3.54-5.0) 1.04 (0.78-1.39) P-trend <0.0001 0.527 <0.0001 0.783 BMI classification

d


Continued….

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a%(95% CI) ARR


a%(95% CI) ARR

b(95% CI)

Physical activities

Weighted total sessions exercise-related physical activity (average between 2005 and 2009) 0-7 ses/we 198 6.3 (5.5-7.1) 1 162 2.2 (1.8-2.6) 1 8-14 ses/w 589 5.2 (4.8-5.6) 0.9 (0.76-1.07) 352 2.1 (1.9-2.3) 1.0 (0.82-1.23)

≥15 ses/w 380 4.4 (4.0-5.0) 0.78 (0.65-0.95) 119 2.2 (1.8-2.6) 1.0 (0.77-1.3)

P-trend <0.0001 <0.029 0.905 1.0

Underlying diseases

Diabetes mellitus

No 1251 5.0 (4.7-5.27) 1 674 2.1 (1.9-2.26) 1 Yes 55 18.3 (13.9-22.7) 1.81 (1.29-2.52) 16 10.7 (5.7-15.8) 2.54 (1.41-4.56)

High lipids

No 983 4.4 (4.13-4.67) 1 576 1.9 (1.76-2.1) 1 Yes 323 10.8 (9.7-11.9) 1.4 (1.21-1.63) 114 5.4 (4.47-6.4) 1.38 (1.09-1.75)

Kidney diseases

No 1248 5.1 (4.8-5.33) 1 659 2.1 (1.9-2.26) 1 Yes 58 9.6 (7.2-11.9) 1.62 (1.19-2.2) 31 3.9 (2.52-5.2) 1.77 (1.19-2.63)

Personal behaviours

Smoking status Never 506 4.1 (3.7-4.4) 1 617 2.1 (1.9-2.23) 1 Ex-smoker 496 6.6 (6.0-7.13) 1.15 (1.0-1.32) 37 3.2 (2.2-4.22) 1.28 (0.88-1.87) Cur-smokerf 276 5.8 (5.16-6.5) 1.22 (1.04-1.44) 8 3.1 (0.97-5.2) 1.54 (0.74-3.2) P-trend <0.0001 <0.032 <0.008 0.23

Drinking status

Never 105 3.9 (3.2-4.7) 1 268 2.1 (1.8-2.32) 1 Ex-drinker 155 5.7 (4.85-6.6) 0.98 (0.74-1.3) 50 2.2 (1.6-2.85) 1.14 (0.82-1.59) Occ- drinkerg 821 4.8 (4.45-5.1) 1.0 (0.8-1.25) 352 2.1 (1.9-2.36) 1.14 (0.96-1.36) Reg- drinker

h 212 8.6 (7.5-9.7) 1.61 (1.23-2.11) 9 4.7 (1.66-7.7) 1.83 (0.86-3.9)

P-trend <0.0001 <0.0001 0.471 0.254


Instant food


bAdjusted relative risks were calculated from multi-variate logistic regression models of hypertension adjusted for age, marital status, education, income, BMI category, underlying diseases, personal behaviours. cAt the time of the survey in 2005, US$1 = 42 Thai baht dAsian standard BMI classification eSessions / week fCurrent-smoker gOccasional drinker hRegular drinker

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Health-risk factors and the incidence of hypertension: 4-year

prospective findings from a national cohort of 60,569 Thai open

university students

Prasutr Thawornchaisit, School of Medicine, Faculty of Health Science, University of

Queensland, 288 Herston Road, Herston, Brisbane, QLD, 4006 Australia and Department of

Medicine, Lerdsin Hospital, Silom road, Bangrak, Bangkok, 10500 Thailand


Telephone: 662-585-8015

Fax: 662-912-0121

Prasutr Thawornchaisit, MD, MPH1, Ferdinandus de Looze, MBBS, MSc

1, Christopher M Reid,

PhD2, Sam-ang Seubsman, PhD

3, Adrian Sleigh, MD

4, Thai Cohort Study Team*

1 School of Medicine, University of Queensland, Brisbane, Australia, 2 School of Public Health

and Preventive Medicine, Monash University, Melbourne, Australia, 3 School of Human

Ecology, Sukhothai Thammathirat Open University, Nonthaburi, Thailand, 4 National Centre for

Epidemiology and Population Health, ANU College of Medicine, Biology and Environment, The

Australian National University, Canberra, Australia.

*Thailand: Jaruwan Chokhanapitak, Suttanit Hounthasarn, Suwanee Khamman, Daoruang

Pandee, Suttinan Pangsap, Tippawan Prapamontol, Janya Puengson, Sam-ang Seubsman,

Boonchai Somboonsook, Nintita Sripaiboonkij, Pathumvadee Somsamai, Prasutr

Thawornchaisit, Duangkae Vilainerun, Wanee Wimonwattanaphan, Cha-aim Pachanee, Arunrat

Tangmunkongvorakul, Benjawan Tawatsupa, Wimalin Rimpeekool.

Australia: Chris Bain, Emily Banks, Cathy Banwell, Bruce Caldwell, Gordon Carmichael, Tarie

Dellora, Jane Dixon, Sharon Friel, David Harley, Matthew Kelly, Tord Kjellstrom, Lynette Lim,

Anthony McMichael, Tanya Mark, Adrian Sleigh, Lyndall Strazdins, Vasoontara

Yiengprugsawan, Susan Jordan, Janneke Berecki-Gisolf, Rod McClure.


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Word Count: 4483

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Section/Topic Item




Introduction



Methods



collection

5




applicable

5

Data sources/

measurement



5-6


Study size 10 Explain how the study size was arrived at 4-5


why

5-6






Results 7

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4-5




confounders

5






7




Discussion


Limitations



12


Other information



13





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1




1, Christopher M

Reid, PhD2, Sam-ang Seubsman, PhD



1 School of Medicine, University of Queensland, Brisbane, Australia; 2 School of Public Health and

Preventive Medicine, Monash University, Melbourne, Australia; 3 School of Human Ecology, Sukhothai

Thammathirat Open University, Nonthaburi, Thailand; 4 National Centre for Epidemiology and Population



*Thai Cohort Study Team





Rimpeekool.





Corresponding author: Prasutr Thawornchaisit, School of Medicine, Faculty of Health Science, University

of Queensland, 288 Herston Road, Herston, Brisbane, QLD, 4006 Australia and Department of Medicine,

Lerdsin Hospital, Silom road, Bangrak, Bangkok, 10500 Thailand

Email: [email protected] Telephone: 66-2-585-8015 Fax: 66-2-912-0121


Key words: hypertension; health-risks; cohort; Thailand; socioeconomic; body mass index; smoking;

drinking; physical activity

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Abstract

Objective



Design


Thai Cohort Study (TCS) from 2005 to 2009.

Setting




Study participants



Measures



Results





Conclusion





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Introduction

























Methods

Study population

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Risk Factors

















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Results





























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Discussion


























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income pattern.



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Factor

n % n % P-valuea

Demographic data


b


c <0.0001





e (baht)

d <0.001



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Demography

Age group

≤30 y 279 2.5 (2.2-2.8) 1 215 1.1 (0.97-1.3) 1 31-40 y 484 5.3 (4.8-5.7) 1.66 (1.39-1.98) 245 2.5 (2.23-2.9) 1.93 (1.56-2.39) >40 y 543 11.2 (10.3-12.1) 3.13 (2.57-3.81) 230 6.8 (6.0-7.7) 4.2 (3.26-5.42) P-trend <0.0001 <0.0001 <0.0001 <0.0001


No 368 3.3 (3.0-3.7) 1 303 1.6 (1.43-1.8) 1 Yes 896 6.6 (6.17-7.0) 0.97 (0.83-1.12) 368 2.9 (2.65-3.2) 1.22 (1.03-1.45)


Education level


BMI classificationd





Continued….

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a%(95% CI) ARR


a%(95% CI) ARR

b(95% CI)

Physical activities


≥15 ses/w 380 4.4 (4.0-5.0) 0.78 (0.65-0.95) 119 2.2 (1.8-2.6) 1.0 (0.77-1.3)

P-trend <0.0001 <0.029 0.905 1.0

Underlying diseases

Diabetes mellitus

No 1251 5.0 (4.7-5.27) 1 674 2.1 (1.9-2.26) 1 Yes 55 18.3 (13.9-22.7) 1.81 (1.29-2.52) 16 10.7 (5.7-15.8) 2.54 (1.41-4.56)

High lipids

No 983 4.4 (4.13-4.67) 1 576 1.9 (1.76-2.1) 1 Yes 323 10.8 (9.7-11.9) 1.4 (1.21-1.63) 114 5.4 (4.47-6.4) 1.38 (1.09-1.75)

Kidney diseases

No 1248 5.1 (4.8-5.33) 1 659 2.1 (1.9-2.26) 1 Yes 58 9.6 (7.2-11.9) 1.62 (1.19-2.2) 31 3.9 (2.52-5.2) 1.77 (1.19-2.63)

Personal behaviours

Smoking status

Never 506 4.1 (3.7-4.4) 1 617 2.1 (1.9-2.23) 1 Ex-smoker 496 6.6 (6.0-7.13) 1.15 (1.0-1.32) 37 3.2 (2.2-4.22) 1.28 (0.88-1.87) Cur-smokerd 276 5.8 (5.16-6.5) 1.22 (1.04-1.44) 8 3.1 (0.97-5.2) 1.54 (0.74-3.2) P-trend <0.0001 <0.032 <0.008 0.23

Drinking status


f 212 8.6 (7.5-9.7) 1.61 (1.23-2.11) 9 4.7 (1.66-7.7) 1.83 (0.86-3.9)

P-trend <0.0001 <0.0001 0.471 0.254


Instant food



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Journal: BMJ Open

Manuscript ID: bmjopen-2013-002826.R2


Date Submitted by the Author: 31-May-2013




Epidemiology

Secondary Subject Heading: Cardiovascular medicine, Public health



BMJ Open on F


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1







Telephone: 662-585-8015

Fax: 662-912-0121








*Thailand: Jaruwan Chokhanapitak, Suttanit Hounthasarn, Suwanee Khamman, Daoruang Pandee, Suttinan




Rimpeekool.







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Abstract

Objective



Design


Thai Cohort Study (TCS) from 2005 to 2009

Setting




Study participants



Measures



Results





Conclusion





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Article summary

Article focus

In a large Thai Cohort Study, we measured the effect of exposure to health-risk factors recorded in 2005 on

the incidence rate of hypertension over the following 4 years. This is part of a study of the health-risk

transition underway in Thailand. We investigated socio-demographic factors, co-morbidity, body size,

physical activity and health behaviour. Cohort members are Open University students, live nationwide, are

well educated and of modest means, representing the next generation of adult Thais.

Key Messages

Overall, the incidence of self-reported hypertension in Thai adults was 3.5% with the rate for males much

higher than females (5.2% vs. 2.1%). In both sexes hypertension incidence was associated with age, higher

body mass index, kidney disease, diabetes and high lipids, but not with socioeconomic status.

Marriage or partnering increased risk of hypertension in females but not in males. Planned physical activity,

averaged across the 4-year follow-up, protected males: ≥15 sessions /week associated with lower incidence

of hypertension. However, this was not observed in females.

In males, current-smokers had a higher risk of developing hypertension than non-smokers while in females


risk of incident hypertension.

Strengths

In Thailand, this cohort constitutes the largest longitudinal study of health-risk factors and hypertension

development. As a consequence, many independent risk factors for hypertension in Thais can be identified.

Our cohort represents Thais well in geography and socio-economy so the results reflect trends of the health-

risk transition in the population.

Limitations

Our study relies on self-report. There may be recall and reporting errors. Some risk factors may take more

than four years to produce hypertension and will manifest as the cohort ages.

Introduction

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Methods

Study population




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Risk Factors










baht), medium (30,001-60,000 baht) and high (>60,000 baht).










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calculated from self-reported height in metres and weight in kilograms as weight/height2. It was divided into

4 categories as follows according to Asian criteria:[8 13-16] underweight (BMI <18.5), normal (18.5 to




















Results





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the risk of hypertension in females. However, this was not noticed in male. Educational attainment and

personal income had no influence on the risk of hypertension in both sexes. In males and females, the risk of

hypertension increased with an increased BMI. The risk of hypertension increased in both males and females

who had diabetes mellitus, high blood lipids and kidney disease.















Discussion

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income pattern.







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period. As a consequence, independent risk factors for hypertension in Thais can be identified. With the high

initial non-response rate and participants drawn from only one university distance-learning students enrolled

at Sukhothai Thammathirat Open University may not be representative of the Thai people or next generation

of Thais. However, our nationwide cohort represents STOU students well and also represents the Thai

population well in geography and socio-economy [9] so the results to some extent reflect the trend of health-

risk transition in the Thai population. Indeed, STOU students, with better education attainment combined

with their representative incomes and geographical location, are likely to represent the next generation of

Thais. It would be reasonable to conclude that our 4-year follow-up results may indicate future hypertension

trends for Thai people.















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Data sharing: No additional data available.

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Factor

n % n % P-valuea

Demographic data


b


c <0.0001





e (baht)

d <0.001



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Males Females

HT(n) Incia%(95% CI) ARR


a%(95% CI) ARR

b(95% CI)

Participants 1306 5.2 (4.9-5.4) 690 2.1 (2.0-2.3)

Demography

Age group

≤30 y 279 2.5 (2.2-2.8) 1 215 1.1 (0.97-1.3) 1 31-40 y 484 5.3 (4.8-5.7) 1.66 (1.39-1.98) 245 2.5 (2.23-2.9) 1.93 (1.56-2.39) >40 y 543 11.2 (10.3-12.1) 3.13 (2.57-3.81) 230 6.8 (6.0-7.7) 4.2 (3.26-5.42) P-trend <0.0001 <0.0001 <0.0001 <0.0001


No 368 3.3 (3.0-3.7) 1 303 1.6 (1.43-1.8) 1 Yes 896 6.6 (6.17-7.0) 0.97 (0.83-1.12) 368 2.9 (2.65-3.2) 1.22 (1.03-1.45)


Education level

High school 697 5.2 (4.8-5.6) 1 303 2.3 (2.05-2.57) 1 Diploma 276 4.8 (4.25-5.4) 1.0 (0.86-1.17) 180 1.8 (1.57-2.1) 0.81 (0.66-0.99) University 331 5.4 (4.8-5.9) 0.93 (0.8-1.1) 204 2.2 (1.9-2.51) 0.87 (0.71-1.07) P-trend 0.83 0.61 0.463 0.1 Personal monthly income (baht)c ≤7000 268 3.3 (2.95-3.7) 1 217 1.6 (1.36-1.8) 1 7001-10000 229 4.0 (3.45-4.5) 1.0 (0.81-1.2) 142 1.9 (1.57-2.2) 1.1 (0.87-1.37) 10001-20000 497 6.6 (6.0-7.14) 1.1 (0.91-1.31) 196 2.7 (2.35-3.1) 0.97 (0.77-1.23) >20000 289 8.4 (7.46-9.3) 1.0 (0.8-1.25) 122 4.3 (3.54-5.0) 1.04 (0.78-1.39) P-trend <0.0001 0.527 <0.0001 0.783 BMI classification

d


Continued….

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a%(95% CI) ARR


a%(95% CI) ARR

b(95% CI)

Physical activities

Weighted total sessions exercise-related physical activity (average between 2005 and 2009) 0-7 ses/we 198 6.3 (5.5-7.1) 1 162 2.2 (1.8-2.6) 1 8-14 ses/w 589 5.2 (4.8-5.6) 0.9 (0.76-1.07) 352 2.1 (1.9-2.3) 1.0 (0.82-1.23)

≥15 ses/w 380 4.4 (4.0-5.0) 0.78 (0.65-0.95) 119 2.2 (1.8-2.6) 1.0 (0.77-1.3)

P-trend <0.0001 <0.029 0.905 1.0

Underlying diseases

Diabetes mellitus

No 1251 5.0 (4.7-5.27) 1 674 2.1 (1.9-2.26) 1 Yes 55 18.3 (13.9-22.7) 1.81 (1.29-2.52) 16 10.7 (5.7-15.8) 2.54 (1.41-4.56)

High lipids

No 983 4.4 (4.13-4.67) 1 576 1.9 (1.76-2.1) 1 Yes 323 10.8 (9.7-11.9) 1.4 (1.21-1.63) 114 5.4 (4.47-6.4) 1.38 (1.09-1.75)

Kidney diseases

No 1248 5.1 (4.8-5.33) 1 659 2.1 (1.9-2.26) 1 Yes 58 9.6 (7.2-11.9) 1.62 (1.19-2.2) 31 3.9 (2.52-5.2) 1.77 (1.19-2.63)

Personal behaviours

Smoking status Never 506 4.1 (3.7-4.4) 1 617 2.1 (1.9-2.23) 1 Ex-smoker 496 6.6 (6.0-7.13) 1.15 (1.0-1.32) 37 3.2 (2.2-4.22) 1.28 (0.88-1.87) Cur-smokerf 276 5.8 (5.16-6.5) 1.22 (1.04-1.44) 8 3.1 (0.97-5.2) 1.54 (0.74-3.2) P-trend <0.0001 <0.032 <0.008 0.23

Drinking status

Never 105 3.9 (3.2-4.7) 1 268 2.1 (1.8-2.32) 1 Ex-drinker 155 5.7 (4.85-6.6) 0.98 (0.74-1.3) 50 2.2 (1.6-2.85) 1.14 (0.82-1.59) Occ- drinkerg 821 4.8 (4.45-5.1) 1.0 (0.8-1.25) 352 2.1 (1.9-2.36) 1.14 (0.96-1.36) Reg- drinker

h 212 8.6 (7.5-9.7) 1.61 (1.23-2.11) 9 4.7 (1.66-7.7) 1.83 (0.86-3.9)

P-trend <0.0001 <0.0001 0.471 0.254


Instant food



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Int J Epidemiol 2008;37(2):266-72.


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BMC Public Health 2011;11(762):1-14.


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cohort of 15-87-year-old open university students in Thailand. J Epidemiol 2010;20(1):13-20.

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countries. Population health metrics 2009;7:1-15.


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Section/Topic Item




Introduction



Methods



collection

5




applicable

5

Data sources/

measurement



5-6


Study size 10 Explain how the study size was arrived at 4-5


why

5-6






Results 7

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4-5




confounders

5






7




Discussion


Limitations



12


Other information



13





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1




1, Christopher M

Reid, PhD2, Sam-ang Seubsman, PhD



1 School of Medicine, University of Queensland, Brisbane, Australia; 2 School of Public Health and

Preventive Medicine, Monash University, Melbourne, Australia; 3 School of Human Ecology, Sukhothai

Thammathirat Open University, Nonthaburi, Thailand; 4 National Centre for Epidemiology and Population



*Thai Cohort Study Team





Rimpeekool.





Corresponding author: Prasutr Thawornchaisit, School of Medicine, Faculty of Health Science, University

of Queensland, 288 Herston Road, Herston, Brisbane, QLD, 4006 Australia and Department of Medicine,

Lerdsin Hospital, Silom road, Bangrak, Bangkok, 10500 Thailand

Email: [email protected] Telephone: 66-2-585-8015 Fax: 66-2-912-0121


Key words: hypertension; health-risks; cohort; Thailand; socioeconomic; body mass index; smoking;

drinking; physical activity

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Abstract

Objective



Design


Thai Cohort Study (TCS) from 2005 to 2009.

Setting




Study participants



Measures



Results





Conclusion





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Introduction

























Methods

Study population

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Risk Factors

















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Results





























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Discussion


























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income pattern.



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Factor

n % n % P-valuea

Demographic data


b


c <0.0001





e (baht)

d <0.001



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Demography

Age group

≤30 y 279 2.5 (2.2-2.8) 1 215 1.1 (0.97-1.3) 1 31-40 y 484 5.3 (4.8-5.7) 1.66 (1.39-1.98) 245 2.5 (2.23-2.9) 1.93 (1.56-2.39) >40 y 543 11.2 (10.3-12.1) 3.13 (2.57-3.81) 230 6.8 (6.0-7.7) 4.2 (3.26-5.42) P-trend <0.0001 <0.0001 <0.0001 <0.0001


No 368 3.3 (3.0-3.7) 1 303 1.6 (1.43-1.8) 1 Yes 896 6.6 (6.17-7.0) 0.97 (0.83-1.12) 368 2.9 (2.65-3.2) 1.22 (1.03-1.45)


Education level


BMI classificationd





Continued….

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a%(95% CI) ARR


a%(95% CI) ARR

b(95% CI)

Physical activities


≥15 ses/w 380 4.4 (4.0-5.0) 0.78 (0.65-0.95) 119 2.2 (1.8-2.6) 1.0 (0.77-1.3)

P-trend <0.0001 <0.029 0.905 1.0

Underlying diseases

Diabetes mellitus

No 1251 5.0 (4.7-5.27) 1 674 2.1 (1.9-2.26) 1 Yes 55 18.3 (13.9-22.7) 1.81 (1.29-2.52) 16 10.7 (5.7-15.8) 2.54 (1.41-4.56)

High lipids

No 983 4.4 (4.13-4.67) 1 576 1.9 (1.76-2.1) 1 Yes 323 10.8 (9.7-11.9) 1.4 (1.21-1.63) 114 5.4 (4.47-6.4) 1.38 (1.09-1.75)

Kidney diseases

No 1248 5.1 (4.8-5.33) 1 659 2.1 (1.9-2.26) 1 Yes 58 9.6 (7.2-11.9) 1.62 (1.19-2.2) 31 3.9 (2.52-5.2) 1.77 (1.19-2.63)

Personal behaviours

Smoking status

Never 506 4.1 (3.7-4.4) 1 617 2.1 (1.9-2.23) 1 Ex-smoker 496 6.6 (6.0-7.13) 1.15 (1.0-1.32) 37 3.2 (2.2-4.22) 1.28 (0.88-1.87) Cur-smokerd 276 5.8 (5.16-6.5) 1.22 (1.04-1.44) 8 3.1 (0.97-5.2) 1.54 (0.74-3.2) P-trend <0.0001 <0.032 <0.008 0.23

Drinking status


f 212 8.6 (7.5-9.7) 1.61 (1.23-2.11) 9 4.7 (1.66-7.7) 1.83 (0.86-3.9)

P-trend <0.0001 <0.0001 0.471 0.254


Instant food



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References



2003;42(6):1206-52 doi: 10.1161/01.HYP.0000107251.49515.c2



income countries. Curr Probl Cardiol 2010;35(2):72-115 doi: S0146-2806(09)00127-3 [pii]




management of hypertension. J Hypertens 2003;21(11):1983-92 doi:

10.1097/01.hjh.0000084751.37215.d2[published Online First: Epub Date]|.



III-IV. J Hypertens 2012;30(9):1734-42 doi: 10.1097/HJH.0b013e3283568158[published Online

First: Epub Date]|.






2004. J Hypertens 2008;26(2):191-8 doi: 10.1097/HJH.0b013e3282f09f57




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