This article was downloaded by: [Flinders University of South Australia]On: 07 October 2014, At: 22:20Publisher: RoutledgeInforma Ltd Registered in England and Wales Registered Number: 1072954 Registeredoffice: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

Behavioral Sleep MedicinePublication details, including instructions for authors andsubscription information:http://www.tandfonline.com/loi/hbsm20

Sleep Duration and Quality of Life inYoung Rural Chinese ResidentsHelen F. K. Chiu a , Yu-Tao Xiang a b , Jing Dai c , Sandra S. M. Chan a

, Xin Yu d , Gabor S. Ungvari e f & Eric D. Caine ga Department of Psychiatry , Chinese University of Hong Kong , HongKong SAR, Chinab Beijing Anding Hospital, Capital Medical University , Beijing , Chinac Shenzhen Institute of Mental Health, Shenzhen Kangning Hospital,Shenzhen Mental Health Center , Shenzhen , Chinad Institute of Mental Health, Peking University , Beijing , Chinae School of Psychiatry and Clinical Neurosciences, University ofWestern Australia , Perth , Australiaf The University of Notre Dame Australia/Marian Centre , Perth ,Australiag Center for the Study and Prevention of Suicide, Department ofPsychiatry , University of Rochester Medical Center , Rochester , NYPublished online: 05 Mar 2013.

To cite this article: Helen F. K. Chiu , Yu-Tao Xiang , Jing Dai , Sandra S. M. Chan , Xin Yu , Gabor S.Ungvari & Eric D. Caine (2013) Sleep Duration and Quality of Life in Young Rural Chinese Residents,Behavioral Sleep Medicine, 11:5, 360-368, DOI: 10.1080/15402002.2013.764524

To link to this article: http://dx.doi.org/10.1080/15402002.2013.764524

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the“Content”) contained in the publications on our platform. However, Taylor & Francis,our agents, and our licensors make no representations or warranties whatsoever as tothe accuracy, completeness, or suitability for any purpose of the Content. Any opinionsand views expressed in this publication are the opinions and views of the authors,and are not the views of or endorsed by Taylor & Francis. The accuracy of the Contentshould not be relied upon and should be independently verified with primary sourcesof information. Taylor and Francis shall not be liable for any losses, actions, claims,proceedings, demands, costs, expenses, damages, and other liabilities whatsoever orhowsoever caused arising directly or indirectly in connection with, in relation to or arisingout of the use of the Content.

This article may be used for research, teaching, and private study purposes. Anysubstantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions

Dow

nloa

ded

by [

Flin

ders

Uni

vers

ity o

f So

uth

Aus

tral

ia]

at 2

2:20

07

Oct

ober

201

4

Behavioral Sleep Medicine, 11:360–368, 2013

Copyright © Taylor & Francis Group, LLC

ISSN: 1540-2002 print/1540-2010 online

DOI: 10.1080/15402002.2013.764524

Sleep Duration and Quality of Life in YoungRural Chinese Residents

Helen F. K. ChiuDepartment of Psychiatry

Chinese University of Hong Kong, Hong Kong SAR, China

Yu-Tao XiangDepartment of Psychiatry

Chinese University of Hong Kong, Hong Kong SAR, China

Beijing Anding Hospital

Capital Medical University, Beijing, China

Jing DaiShenzhen Institute of Mental Health

Shenzhen Kangning Hospital, Shenzhen Mental Health Center, Shenzhen, China

Sandra S. M. ChanDepartment of Psychiatry

Chinese University of Hong Kong, Hong Kong SAR, China

Xin YuInstitute of Mental Health

Peking University, Beijing, China

Gabor S. UngvariSchool of Psychiatry and Clinical Neurosciences

University of Western Australia, Perth, Australia

The University of Notre Dame Australia/Marian Centre, Perth, Australia

Eric D. CaineCenter for the Study and Prevention of Suicide

Department of Psychiatry

University of Rochester Medical Center, Rochester, NY

Correspondence should be addressed to Yu-Tao Xiang, Department of Psychiatry, Chinese University of Hong

Kong, Ground Floor, Multicentre, Tai Po Hospital, Tai Po, N.T., Hong Kong, China. E-mail: xyutly@gmail.com

360

Dow

nloa

ded

by [

Flin

ders

Uni

vers

ity o

f So

uth

Aus

tral

ia]

at 2

2:20

07

Oct

ober

201

4

CHIU ET AL. 361

The aim of this study was to determine the mean total sleep time (TST) and the relation between

sleep duration (short sleep: < 7 hr per day; medium sleep: 7–8 hr per day; and long sleep:

> 8 hr per day) and quality of life (QOL) in young Chinese rural residents. A sample of 1,632

participants was recruited in Mianyang, Sichuan province and interviewed. Expected and actual

TSTs were asked using standardized questions. QOL was measured with the Chinese version of the

World Health Organization Quality of Life Schedule-Brief. In the full sample, the mean expected

TST was 8:8 ˙ 1:3 hr, and the mean actual TST was 8:3 ˙ 1:4 hr. Multivariate analyses revealed

that compared to medium sleepers, short sleepers had lower QOL in the physical, psychological,

and environmental domains, whereas long sleepers had higher QOL in the environmental domain.

Being short or long sleepers was not associated with more major medical conditions. Given the

significant associations between short sleep and poor QOL, more attention should be paid to young

Chinese rural residents with short sleep.

Compared with those who sleep 7 to 8 hr daily, both short and long sleepers have an increased

total mortality risk (Heslop, Smith, Metcalfe, Macleod, & Hart, 2002; Youngstedt & Kripke,

2004), sleep complaints (Grandner & Kripke, 2004; Kripke et al., 2001), and depression

(Grandner & Drummond, 2007). In recent years, the association between sleep duration and

quality of life (QOL) has been gaining attention.

Several studies have explored the association between sleep duration and QOL in Western

settings. For example, Faubel et al. (2009) examined 3,834 people aged 60 and over and found

that both short and long sleep were associated with poor QOL. In contrast, Jean-Louis, Kripke,

and Ancoli-Israel (2000) interviewed 273 people aged 40 to 64 and found no association

between sleep duration and QOL.

Preliminary evidence indicates that cross-cultural and ethnic differences exist in both QOL

(Warner et al., 1998) and sleep problems (Gureje, Makanjuola, & Kola, 2007; Ohayon &

Partinen, 2002). Therefore, the findings reported from Western settings may not be applicable

to those with different ethnic and cultural backgrounds.

In China, the suicide rates in rural Chinese women and men aged 15 to 34 years are

quite high (38 and 23 per 100,000, respectively; Phillips, Li, & Zhang, 2002). Given that

adolescent suicidal behaviors are closely associated with sleep problems, which, in turn, could

cause a number of health problems (Grandner & Drummond, 2007; Tamakoshi & Ohno,

2004; Youngstedt & Kripke, 2004), it is important to understand the sleep patterns in this

population.

To date, no study has examined sleep duration and its relation to QOL in young Chinese

rural residents. This study set out to explore (a) the expected and actual mean total sleep time

(TST) and (b) the relations between short, medium, and long sleep and QOL in young Chinese

rural residents aged 16 (the minimum statutory age of independent consent in China) through

34 years.

METHOD

Participants and Sampling

The study was part of a large-scale epidemiologic survey on suicidal behavior and sleep

disturbance in young Chinese rural residents in the rural area of Mianyang, Sichuan province,

Dow

nloa

ded

by [

Flin

ders

Uni

vers

ity o

f So

uth

Aus

tral

ia]

at 2

2:20

07

Oct

ober

201

4

362 SLEEP DURATION IN RURAL CHINESE RESIDENTS

China (Dai et al., 2011). The study examined a stratified, multistage, and systematic sample

of residents aged 16 to 34. Besides participants’ ages and places of residence, the only

other inclusion criterion was the ability to communicate with the researchers to complete

the interview. Mianyang was chosen as the study site as it is a typical rural area in China in

terms of financial and living conditions, and also the enormous number of outgoing migrant

workers.

China’s administrative division is a three-tier system that consists of a hierarchy of provinces,

counties or cities, and towns. A town is composed of a group of villages (rural) and a small

township area (urban). The details of the recruitment process have been described elsewhere

(Dai et al., 2011). The key procedures were as follows: (a) Of the 277 towns in Mianyang

district, Sichuan province, 24 towns and 266 surrounding villages were randomly selected, of

which 11 villages were again randomly selected as study sites. One village was randomly chosen

for pilot testing and as a training site for the interviewers. From the other 10 villages, 3,008

participants aged 16 to 34 were identified using the comprehensive list of residents included

in the Chinese household registration system (hukou; the hukou system was implemented

in China in the 1950s to improve migration control and economic planning, and it is still

functioning). (b) The field work was carried out in two waves in late 2005 and early 2006

to maximize the recruitment of participants, particularly migrant workers who returned home

only around the time of the Chinese New Year. Figure 1 depicts the sampling process of

the study.

We recruited 24 interviewers from experienced Centers for Disease Control and Prevention

field staff, who had completed 7 days of intensive training and interrater reliability exercises.

The selection of interviewers was based on training performance, the results of the interrater

reliability testing, and a paper examination. The interviews were conducted in locations that

were convenient for the participants.

Assessment Tools

Socio-demographic data were collected using a questionnaire designed for the study that in-

quired about TST; major medical conditions affecting the cardiovascular, respiratory, digestive,

hematological, endocrine, urinary, connective tissue, and nervous systems; and psychiatric

disorders. Perceptions of financial situations were rated as poor, moderate, or good based on

participants’ self-appraisals. To measure expected and actual TST in the past month, participants

were asked the following questions: “How many hours of sleep per night do you think you

need?,” and “How many hours do you sleep each night on average?” There is no gold standard

definition of short and long sleepers. In this study, we used the criteria proposed by Heslop

et al. (2002), which have also been used in other investigations (Grandner & Kripke, 2004;

Xiang et al., 2009): short sleep: < 7 hr per day; medium sleep: 7 to 8 hr per day; and long

sleep: > 8 hr per day.

QOL is defined as “individuals’ perceptions of their position in life in the context of the

culture and value systems in which they live and in relation to their goals, expectations,

standards and concerns” (World Health Organization [WHO], 1998, p. 551). QOL is a broad

concept that consists of four main domains: physical health, psychological condition, social

relationships, and relation to the environment. In this study, all four domains of QOL were

assessed with the Chinese version of the WHO Quality of Life Schedule–Brief (WHO, 1995).

Dow

nloa

ded

by [

Flin

ders

Uni

vers

ity o

f So

uth

Aus

tral

ia]

at 2

2:20

07

Oct

ober

201

4

CHIU ET AL. 363

FIGURE 1 Recruitment of participants. aHukou is the Chinese household registration system.

Dow

nloa

ded

by [

Flin

ders

Uni

vers

ity o

f So

uth

Aus

tral

ia]

at 2

2:20

07

Oct

ober

201

4

364 SLEEP DURATION IN RURAL CHINESE RESIDENTS

The study protocol was approved by the Survey and Behavioral Ethics Committee of the

Chinese University of Hong Kong and the Human Research and Ethics Committees of local

participating institutions. Written consent was obtained from all participants.

Statistical Analysis

First, comparisons of the basic socio-demographic and clinical characteristics of the different

sleepers were performed using one-way analyses of variance or chi-square tests, as appropriate.

Second, analyses of covariance were used to compare the physical, psychological, social, and

environmental domains of QOL between different sleepers, after adjusting for the potential

confounding variables including age, gender, marital status, education, employment, perceived

financial situation, and psychiatric disorders and major medical conditions. Third, the inde-

pendent associations between sleep duration and presence of major medical conditions were

explored using multiple logistic regression (the “Enter” method), with the presence of major

medical conditions as the dependent variable and sleep duration as the independent variable

after controlling for age, gender, marital status, education, financial situation, employment, psy-

chiatric disorders, and QOL by entering them as covariates. The level of statistical significance

was set at .01 (two-tailed) to reduce the risk of Type 1 error due to multiple tests.

RESULTS

Figure 1 depicts the study’s sampling results. Of the 3,008 names generated from the hukou list,

1,284 were either living away permanently or were migrant workers who did not return home

for prolonged periods and, thus, were not contactable. A total of 1,689 people were contacted,

and 1,632 were finally included in this study; thus, the response rate was 97%. The actual

TST hours were 5:8 ˙ 0:8, 7:8 ˙ 0:4, and 9:6 ˙ 0:9 in the short, medium, and long sleepers,

respectively. Table 1 shows the basic socio-demographic and clinical characteristics of the

participants. Univariate analyses revealed significant differences between the three groups with

respect to age, perception of financial situation, and the presence of major medical conditions.

After controlling for potential confounding variables, there were significant differences

between the three groups in terms of physical, psychological, and environmental domains

of QOL. Specifically, compared to medium sleepers, short sleepers had lower QOL in the

physical, psychological, and environmental domains, whereas long sleepers had higher QOL

in the environmental domain (see Table 2).

Multiple logistic regression analysis revealed that after controlling for potential confounding

variables, compared to medium sleepers, being short .p D :01/ or long sleepers .p D :80/

was not significantly associated with more major medical conditions.

DISCUSSION

In this study, we found that in contrast to medium sleepers, short sleepers had lower physical,

psychological, and environmental QOL, whereas long sleepers had higher environmental QOL.

Dow

nloa

ded

by [

Flin

ders

Uni

vers

ity o

f So

uth

Aus

tral

ia]

at 2

2:20

07

Oct

ober

201

4

CHIU ET AL. 365

TABLE 1

Basic Socio-Demographic Characteristics of the Sample

Short

Sleepersa

Medium

Sleepersb

Long

Sleepersc Statistics

Variable n % n % n % �2 df p

Age (in years)d .001

Male 98 49.2 389 50.4 374 56.6 6.60 2 .040

Married 115 57.8 465 60.2 357 54.0 5.70 2 .060

Perception of financial situation 32.90 4 <.001

Poor 45 22.6 125 16.2 67 10.1

Moderate 113 56.8 548 71.0 495 74.9

Good 41 20.6 99 12.8 99 15.0

Education 1.70 4 .800

Illiterate or primary school 1–3 years 25 12.6 81 10.5 83 12.6

Primary school 4–6 years 55 27.6 215 27.8 178 26.9

Junior high school or above 119 59.8 476 61.7 400 60.5

Employment 6.70 4 .200

Farmer 78 39.2 290 37.6 221 33.4

Other 31 15.6 127 16.5 137 20.7

Migrant 90 45.2 355 46.0 303 45.8

Psychiatric disorders 6 3.0 11 1.4 3 0.5 8.80 2 .012

Major medical conditions 50 25.1 110 14.2 81 12.3 20.40 2 <.001

Note. N D 1,632.an D 199. bn D 772. cn D 661. dShort sleepers: M D 27:80, SD D 5:90; medium sleepers: M D 27:30,

SD D 6:10; long sleepers: M D 26:40, SD D 6:20; F.df / D 6:90.2/.

TABLE 2

Independent Association Between Sleep Duration and Quality of Life

Statistics

Short

Sleepers

Medium

Sleepers

Long

Sleepers ANCOVAd

Post Hoc

Analyses

Variable M SD M SD M SD F df p pe pf

Physical QOL 15.70 2.50 16.80 1.90 17.00 1.90 30.50 2, 1,621 <.001 <.001 .060

Psychological 14.40 2.40 15.20 2.10 15.40 2.00 18.30 2, 1,621 <.001 <.001 .050

QOL

Social QOL 15.20 2.50 15.40 2.50 15.50 2.40 0.90 2, 1,621 .400 — —

Environmental 13.20 2.40 13.70 2.30 14.20 2.30 14.30 2, 1,621 <.001 .008 <.001

QOL

Note. N D 1,632. ANCOVA D analysis of covariance; QOL D quality of life.an D 199. bn D 772. cn D 661. dAfter controlling for age, gender, marital status, financial perception, education,

employment, and psychiatric disorders and major medical conditions. eShort versus medium sleepers. fLong versus

medium sleepers.

Dow

nloa

ded

by [

Flin

ders

Uni

vers

ity o

f So

uth

Aus

tral

ia]

at 2

2:20

07

Oct

ober

201

4

366 SLEEP DURATION IN RURAL CHINESE RESIDENTS

As expected, the mean actual TST was shorter than the expected TST (8.3 hr vs. 8.8 hr),

but was considerably longer than previously reported figures from China and other countries.

For example, the mean TST has been reported as 7.8 hr in the general population in Beijing

(Xiang et al., 2009), 7.1 hr in the elderly in Shandong province (Liu & Liu, 2005), 7.1 hr

in an adult working sample in Hong Kong (Ko et al., 2007), 7.8 hr in men and 7.4 hr in

women, respectively, in Japan (Amagai et al., 2004), and 6.99 hr in the general population

in the United States (Grandner & Kripke, 2004). In addition to the diverse methodologies,

including differences in sampling and interview methods and study periods, another important

reason for the longer actual TSTs found in this study may be participants’ rural residencies.

Compared to urban residents, rural residents in China usually have less late nights or shift

work, less evening leisure activities, more outdoor work and physical activities, more exposure

to daylight, and more favorable sleep environments in rural settings, such as lower levels of

noise, which may lead to longer sleep (Gu, Sautter, Pipkin, & Zeng, 2010; Yang, Bu, Dong,

Fan, & Wang, 2009). The results of this study support the notion that industrialization has

considerably shortened sleep duration compared with agricultural societies (Webb & Agnew,

1975).

Short and long sleepers are more likely to have major medical conditions (Alvarez & Ayas,

2004; Ayas et al., 2003; Buysse & Ganguli, 2002; Gottlieb et al., 2005; Patel et al., 2004).

This study, however, failed to find a significant association between short or long sleepers and

increased frequency of medical conditions in young Chinese rural residents. We postulate that

this is related to the young age (16–34 years) of the participants included in this study, as the

long-term adverse effects of short or long sleep on the health of this population would take

time to manifest.

According to the distress/protection model of QOL (Ritsner et al., 2000), QOL is determined

by the interaction between a number distressing and protective factors. Given the significant

association of short sleep with a host of distressing factors, such as poorer physical functioning

(Gottlieb et al., 2005), we can safely assume that there is a similar inverse relation between

short sleep and QOL. In keeping with a previous study (Faubel et al., 2009), we found that

compared with medium sleepers, short sleepers had poorer QOL in the physical, psychological,

and environmental domains. On the other hand, long sleepers had similar scores in the physical,

psychological, and social QOL domains, and even had better QOL scores in the environmental

domain than medium sleepers. The lack of association between long sleepers and lowered QOL

in this sample suggests that the influence of long sleepers on health and QOL is far from clear.

The main limitations of this study are as follows: First, the study involved only one province

of China; therefore, the results may not apply to the whole country. Second, sleep latency

was not measured in this study. Third, there were a considerable number of “uncontactable”

potential participants, most of whom were migrant workers in distant cities, which may have led

to selection bias. Fourth, a number of important variables, such as body mass index, physical

activity, and smoking, were not examined. Fifth, due to the cross-sectional design of the study,

the causality among demographic variables, QOL, and sleep duration could not be determined.

Finally, data of major medical conditions and psychiatric disorders were only collected by self-

report and not based on scrutiny of medical records because having access to medical records

in rural China is not feasible.

In conclusion, considering the significant associations between short sleepers and poor QOL,

more attention should be paid to young Chinese rural residents with short sleep.

Dow

nloa

ded

by [

Flin

ders

Uni

vers

ity o

f So

uth

Aus

tral

ia]

at 2

2:20

07

Oct

ober

201

4

CHIU ET AL. 367

ACKNOWLEDGMENTS

This work was supported, in part, by an unrestricted educational grant from Lundbeck Export

A/S (Helen F. K. Chiu, primary investigator [PI]), by Direct Grant 2041160 from the Chinese

University of Hong Kong (Sandra S. M. Chan, PI), and by Grant D43 TW05814 from the

Fogarty International Center of the National Institutes of Health (Eric D. Caine, PI).

We thank Mianyang Centers for Disease Control and Prevention (CDC) and its regional

CDCs, Dr. Zai-Jin Hou, the key coordinator Zhou Yun (Mianyang CDC), and the numerous

CDC staff, including our interviewers and local helpers from the health system and villages,

for their help with data collection and cleaning. We also thank Tony Leung, Anthony Beckman,

Arthur Watts, and Xin Tu for their assistance with data management and data analysis, and

Kenneth R. Conner for his contribution to the study design, battery development, and data

management. We are grateful to all of the participants who took part in this survey.

REFERENCES

Alvarez, G. G., & Ayas, N. T. (2004). The impact of daily sleep duration on health: A review of the literature. Progress

in Cardiovascular Nursing, 19, 56–59.

Amagai, Y., Ishikawa, S., Gotoh, T., Doi, Y., Kayaba, K., Nakamura, Y., & Kajii, E. (2004). Sleep duration and

mortality in Japan: The Jichi Medical School Cohort Study. Journal of Epidemiology, 14, 124–128.

Ayas, N. T., White, D. P., Al-Delaimy, W. K., Manson, J. E., Stampfer, M. J., Speizer, F. E., : : : Hu, F. B. (2003). A

prospective study of self-reported sleep duration and incident diabetes in women. Diabetes Care, 26, 380–384.

Buysse, D. J., & Ganguli, M. (2002). Can sleep be bad for you? Can insomnia be good? Archives of General Psychiatry,

59, 137–138.

Dai, J., Chiu, H. F., Conner, K. R., Chan, S. S., Hou, Z. J., Yu, X., & Caine, E. D. (2011). Suicidal ideation and

attempts among rural Chinese aged 16–34 years—Socio-demographic correlates in the context of a transforming

China. Journal of Affective Disorders, 130, 438–446.

Faubel, R., Lopez-Garcia, E., Guallar-Castillon, P., Balboa-Castillo, T., Gutierrez-Fisac, J. L., Banegas, J. R., &

Rodriguez-Artalejo, F. (2009). Sleep duration and health-related quality of life among older adults: A population-

based cohort in Spain. Sleep, 32, 1059–1068.

Gottlieb, D. J., Punjabi, N. M., Newman, A. B., Resnick, H. E., Redline, S., Baldwin, C. M., & Nieto, F. J. (2005).

Association of sleep time with diabetes mellitus and impaired glucose tolerance. Archives of Internal Medicine, 165,

863–867.

Grandner, M. A., & Drummond, S. P. (2007). Who are the long sleepers? Towards an understanding of the mortality

relationship. Sleep Medicine Reviews, 11, 341-360.

Grandner, M. A., & Kripke, D. F. (2004). Self-reported sleep complaints with long and short sleep: A nationally

representative sample. Psychosomatic Medicine, 66, 239-241.

Gu, D., Sautter, J., Pipkin, R., & Zeng, Y. (2010). Sociodemographic and health correlates of sleep quality and duration

among very old Chinese. Sleep, 33, 601–610.

Gureje, O., Makanjuola, V. A., & Kola, L. (2007). Insomnia and role impairment in the community: Results from the

Nigerian survey of mental health and wellbeing. Social Psychiatry and Psychiatric Epidemiology, 42, 495–501.

Heslop, P., Smith, G. D., Metcalfe, C., Macleod, J., & Hart, C. (2002). Sleep duration and mortality: The effect of

short or long sleep duration on cardiovascular and all-cause mortality in working men and women. Sleep Medicine,

3, 305–314.

Jean-Louis, G., Kripke, D. F., & Ancoli-Israel, S. (2000). Sleep and quality of well-being. Sleep, 23, 1115–1121.

Ko, G. T., Chan, J. C., Chan, A. W., Wong, P. T., Hui, S. S., Tong, S. D., : : : Chan, C. L. (2007). Association between

sleeping hours, working hours and obesity in Hong Kong Chinese: The “Better Health for Better Hong Kong” health

promotion campaign. International Journal of Obesity, 31, 254–260.

Kripke, D. F., Brunner, R., Freeman, R., Hendrix, S., Jackson, R. D., Masaki, K., & Carter, R. A. (2001). Sleep

complaints of postmenopausal women. Clinical Journal of Women’s Health, 1, 244–252.

Dow

nloa

ded

by [

Flin

ders

Uni

vers

ity o

f So

uth

Aus

tral

ia]

at 2

2:20

07

Oct

ober

201

4

368 SLEEP DURATION IN RURAL CHINESE RESIDENTS

Liu, X., & Liu, L. (2005). Sleep habits and insomnia in a sample of elderly persons in China. Sleep, 28, 1579–1587.

Ohayon, M. M., & Partinen, M. (2002). Insomnia and global sleep dissatisfaction in Finland. Journal of Sleep Research,

11, 339–346.

Patel, S. R., Ayas, N. T., Malhotra, M. R., White, D. P., Schernhammer, E. S., Speizer, F. E., : : : Hu, F. B. (2004). A

prospective study of sleep duration and mortality risk in women. Sleep, 27, 440–444.

Phillips, M. R., Li, X., & Zhang, Y. (2002). Suicide rates in China, 1995–99. Lancet, 359, 835–840.

Ritsner, M., Modai, I., Endicott, J., Rivkin, O., Nechamkin, Y., Barak, P., : : : Ponizovsky, A. (2000). Differences in

quality of life domains and psychopathologic and psychosocial factors in psychiatric patients. Journal of Clinical

Psychiatry, 61, 880–890.

Tamakoshi, A., & Ohno, Y. (2004). Self-reported sleep duration as a predictor of all-cause mortality: Results from the

JACC study, Japan. Sleep, 27, 51–54.

Warner, R., de Girolamo, G., Belelli, G., Bologna, C., Fioritti, A., & Rosini, G. (1998). The quality of life of people

with schizophrenia in Boulder, Colorado, and Bologna, Italy. Schizophrenia Bulletin, 24, 559–568.

Webb, W. B., & Agnew, H. W. (1975). Are we chronically sleep deprived? Bulletin of the Psychonomic Society, 6,

47–48.

World Health Organization. (1995). The World Health Organization Quality of Life assessment (WHOQOL): Position

paper from the World Health Organization. Social Science & Medicine, 41, 1403–1409.

World Health Organization. (1998). Development of the World Health Organization WHOQOL-BREF Quality of Life

assessment. The WHOQOL Group. Psychological Medicine, 28, 551–558.

Xiang, Y. T., Ma, X., Lu, J. Y., Cai, Z. J., Li, S. R., Xiang, Y. Q., : : : Ungvari, G. S. (2009). Relationships of sleep

duration with sleep disturbances, basic socio-demographic factors, and BMI in Chinese people. Sleep Medicine, 10,

1085–1089.

Yang, Q. Z., Bu, Y. Q., Dong, S. Y., Fan, S. S., & Wang, L. X. (2009). A comparison of sleeping problems in

school-age children between rural and urban communities in China. Journal of Paediatrics and Child Health, 45,

414–418.

Youngstedt, S. D., & Kripke, D. F. (2004). Long sleep and mortality: Rationale for sleep restriction. Sleep Medicine

Reviews, 8, 159–174.

Dow

nloa

ded

by [

Flin

ders

Uni

vers

ity o

f So

uth

Aus

tral

ia]

at 2

2:20

07

Oct

ober

201

4