Clinical and Experimental Hypertension, 30:225–231, 2008Copyright © Informa Healthcare USA, Inc.ISSN: 1064-1963 print / 1525-6006 onlineDOI: 10.1080/10641960802068717

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LCEH1064-19631525-6006Clinical and Experimental Hypertension, Vol. 30, No. 3, March 2007: pp. 1–17Clinical and Experimental Hypertension

Home Blood Pressure Measurement May Lead to Less Strict Control of Office Blood Pressure

HBP Measurement and Office BP ControlK. Eto et al. KIMIKA ETO, TAKUYA TSUCHIHASHI, YUKO OHTA, URAN ONAKA, AND MICHIO UENO

Division of Hypertension, Clinical Research Center, National Kyushu MedicalCenter, Fukuoka, Japan

Home blood pressure (HBP) measurement is useful for detecting morning hyperten-sion, white coat as well as masked hypertension. However, target BP levels based onHBP remain unknown. The purpose of the present study was to evaluate the relation-ship between HBP measurement and office BP control status in hypertensive patients.Subjects were a total of 720 hypertensive outpatients (mean age: 64 ± 11 years;females: 57%). Two-time averaged office BP in 2005 were categorized as excellent(<130/85 mmHg), good (³130/85 and <140/90 mmHg), or poor (>140/90 mmHg) con-trol. In all patients, 37% were classified as excellent, 37% as good, and 26% as poorcontrol. A total of 393 (55%) patients regularly measured HBP (HBP group). Morewomen belonged to the HBP group (62 vs. 52%, p < 0.05). The HBP group alsoshowed lower body mass index (23.8 ± 3.3 vs. 24.7 ± 3.4 kg/m2, p < 0.01), lower trig-lyceride (136 ± 78 vs. 158 ± 89 mg/dl, p < 0.01), and lower blood glucose (104 ± 20 vs.118 ± 42 mg/dl, p < 0.01). HBP group showed a significantly higher prevalence ofpoor BP control (33 vs. 23%, p < 0.01) and higher office SBP (134.5 ± 14.5 vs. 131.3 ±11.7 mmHg, p < 0.01) than those who did not measure HBP (non-HBP). In a multi-variate analysis for office SBP, age (partial r = 0.21, p < 0.05) and HBP measurement(partial r = 0.12, p < 0.05) were detected as significant independent variables. Theseresults suggest that HBP measurement may lead to less strict office BP control unlessthe target HBP levels are clearly indicated. Until the recommendations or target HBPlevels are available, we should make an effort to obtain goal office BP.

Keywords home blood pressure measurement, office blood pressure, target bloodpressure, hypertension guideline

The self-measurement of blood pressure (BP) at home, a technique that makes it possibleto obtain multiple measurements under well-controlled conditions, is more reliable thanoffice BP measurement because it avoids both observer and regression dilution biases andeliminates the white-coat effect. Previous cross-sectional studies and a prospective cohortstudy have also shown that HBP measurement has a stronger predictive power for targetorgan damage, morbidity, and mortality than conventional BP measurement (1–5). Because of

Submitted August 31, 2006; revised February 2, 2007; accepted March 11, 2007.Address correspondence to Takuya Tsuchihashi, Division of Hypertension, Clinical Research

Center, National Kyushu Medical Center, Fukuoka, Japan; E-mail: tuti@kyumed.jp

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226 K. Eto et al.

the above benefits, home BP (HBP) measurement is now widely practiced in developed coun-tries. Several national and international guidelines also recommend its use for the better man-agement of hypertension. However, despite the increasing recognition on the importance ofHBP measurement, only a few studies have examined the association between HBP measure-ment and office BP control. The purpose of the present study was to evaluate the relationshipbetween HBP measurement and office BP control status in hypertensive patients.

Methods

Subjects were a total of 720 hypertensive patients who had been followed at our hyperten-sion center. Hypertension was defined as having office SBP ≥140 and/or DBP ≥90 or takingantihypertensive drugs. BP values based on two-time averaged office BP were categorizedas follows: excellent, SBP <130 mmHg and DBP<85 mmHg; good, SBP ≥130 and <140mmHg with DBP<90 mmHg, or DBP ≥85 and <90 mmHg with SBP<140 mmHg; poor:SBP ≥140 mmHg or DBP ≥90 mmHg. These categories were determined based on the targetBP levels indicated by the JSH 2004 guideline. The information whether the patients regu-larly measure HBP and report to the doctors was obtained. The number of antihypertensivedrugs, body mass index (BMI), serum chemistry and urinary salt excretion determined by24-hour urinary collection were assessed. In addition, when the patients were classified asbelonging to the poor group, physicians were asked to report the reasons for poor BP con-trol. Multiple regression analysis for office BP was performed using age, gender, BMI,coexistence of diabetes, and HBP measurement as independent variables. The protocol wasexplained in detail, and informed consent was obtained from each patient.

Statistical Analysis

Results are shown as mean ± SD. Unpaired t test was used for analysis. A chi-square testwas also utilized when appropriate. Multiple regression analysis was performed usingstepwise method (SAS, version 8.02). p values less than 0.05 were considered significant.

Results

Characteristics

In all patients, 37% were classified as excellent, 37% as good, and 26% as poor control. Atotal of 393 (55%) patients regularly measured HBP (HBP group). More women belongedto the HBP group (61% vs. 52%, p < 0.05). As shown in Table 1, HBP group also showedlower BMI (23.8 ± 3.3 vs. 24.7 ± 3.4 kg/m2, p < 0.01), lower triglyceride (136 ± 78 vs.158 ± 89 mg/dl, p < 0.01), and lower blood glucose (104 ± 20 vs. 118 ± 42 mg/dl, p < 0.01).There were no significant differences in age (64 ± 11 vs. 64 ± 11 years) and body weight-adjusted urinary salt excretion (8.6 ± 3.4 vs. 8.9 ± 3.4 g/60kg body weight/day) between theHBP group and the group that did not measure HBP (non-HBP group). The number (1.8 ± 1.2vs. 1.9 ± 1.1) and class of antihypertensive drugs were also similar between groups.

BP Control Status

HBP group showed a significantly higher prevalence of poor BP control (32% vs. 23%,p < 0.01; see Figure 1). Office SBP was significantly higher in the HBP (134.5 ± 14.5mmHg) than in the non-HBP group (131.2 ± 11.7 mmHg, p < 0.01), while office DBP was

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HBP Measurement and Office BP Control 227

lower in the HBP group (see Table 1). In both men and women, the HBP group showedhigher office SBP and lower office DBP than the non-HBP (see Table 2). In men, the HBPgroup took fewer antihypertensive drugs (1.8 ± 1.3 vs. 2.1 ± 1.1, p < 0.05; see Table 2).More subjects who were free of antihypertensive drugs or taking only one drug belongedto the HBP group (chi-square test, p < 0.01) in men but not in women (see Figure 2). In amultiple regression analysis for office SBP, age (partial r = 0.21, p < 0.05) and HBPmeasurement (partial r = 0.12, p < 0.05) were detected as significant independentvariables. Gender, BMI and coexistence of diabetes were not detected as significant deter-minants for office BP.

Table 1Characteristics of patients in Non-HBP and HBP groups

Total Non-HBP HBP

Number 720 327 393Sex (men/women) 308/412 156/171 152/241*Age (years) 64 ± 11 64 ± 11 64 ± 11BMI (kg/m2) 24.2 ± 3.9 24.7 ± 3.4 23.8 ± 3.3**Urinary NaCl excretion (g/day) 8.8 ± 3.5 9.2 ± 3.5 8.5 ± 3.5*(g/day, BW adjusted) 8.7 ± 3.4 8.6 ± 3.4 8.9 ± 3.4Total cholesterol (mg/dl) 204 ± 33 206 ± 32 203 ± 33Triglyceride (mg/dl) 146 ± 84 158 ± 89 136 ± 78**Creatinine (mg/dl) 0.8 ± 0.5 0.8 ± 0.5 0.8 ± 0.4Glucose (mg/dl) 110 ± 33 118 ± 42 104 ± 20**SBP (mmHg) 133.0 ± 13.4 131.2 ± 11.7 134.5 ± 14.5**DBP (mmHg) 73.1 ± 9.5 74.3 ± 9.1 72.1 ± 9.7**Number of antihypertensive

drugs1.9 ± 1.2 1.9 ± 1.1 1.8 ± 1.2

Mean ± SD. Abbreviations: BMI = body mass index, BW = body weight, SBP = systolic bloodpressure, DBP = diastolic blood pressure. *p < 0.05, **p < 0.01 vs. Non-HBP.

Figure 1. Office BP control in non-HBP and HBP group. Office BP values were classified asexcellent, <130/85 mmHg; good, ≥130/85 mmHg and <140/90 mmHg; poor, ≥140/90 mmHg.

Non-HBP Group

Good37%

Excellent40%

Poor23%

HBP Group

Poor32∗∗

%

Good35%

Excellent33%

∗∗p < 0.01 vs. Non-HBP

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228 K. Eto et al.

Reasons for Poor BP Control

In the HBP group, the white-coat effect was the most common reason (40.6%) for poor BPcontrol (see Table 3).

Table 2Comparison of the characteristics between Non-HBP and HBP groups in men and women

Men Women

Non-HBP HBP Non-HBP HBP

Number 156 152 171 241Age (years) 62 ± 11 64 ± 12 65 ± 10 64 ± 10BMI (kg/m2) 24.8 ± 3.0 24.2 ± 2.9 24.6 ± 3.7 23.6 ± 3.5**Urinary NaClexcretion (g/day) 9.5 ± 3.5 9.5 ± 3.9 9.0 ± 3.5 7.8 ± 3.0**(g/day, BW adjusted) 8.5 ± 3.0 8.6 ± 3.5 9.3 ± 3.6 8.6 ± 3.3Total cholesterol (mg/dl) 195 ± 31 195 ± 36 215 ± 30 209 ± 30Triglyceride (mg/dl) 180 ± 100 143 ± 85** 138 ± 74 131 ± 73Creatinine (mg/dl) 1.0 ± 0.4 1.0 ± 0.5 0.7 ± 0.6 0.7 ± 0.3Glucose (mg/dl) 124 ± 49 108 ± 24** 112 ± 34 102 ± 17**SBP (mmHg) 130.4 ± 11.5 134.2 ± 15.3* 132.0 ± 11.8 134.7 ± 14.1*DBP (mmHg) 74.8 ± 9.6 72.0 ± 9.9* 74.0 ± 8.6 72.1 ± 9.6*Number of antihypertensive

drugs2.1 ± 1.1 1.8 ± 1.3* 1.8 ± 1.0 1.8 ± 1.1

Mean ± SD. Abbreviations: BMI = body mass index, BW = body weight, SBP = systolic bloodpressure, DBP = diastolic blood pressure. *p < 0.05, **p < 0.01 vs. Non-HBP.

Figure 2. Comparison of the number of antihypertensive drugs between non-HBP and HBP groupsin men and women.

0%2

1%23

2%43

3%91

4 ≤%31

021

1532

42

371

4 ≤12%

09

1332

53

381

4 ≤5

011

1332

43

361

4 ≤6

Men

Women

Non-HBP Group HBP Group

p < 0.01(chi-square test)

p = 0.89(chi-square test)

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HBP Measurement and Office BP Control 229

Discussion

In the present study, 55% of the patients regularly measured HBP. There was a genderdifference in the prevalence of HBP measurement. Although we do not have the exactfigures, we speculate that men, especially workers, tend to fail to measure their homeBP, while women, especially housewives, may have good compliance to measure homeBP. The HBP group also showed lower BMI, lower triglyceride, and lower bloodglucose in men and women. Krecke et al. reviewed eight German investigations thatreported the prevalence of HBP measurement and found that the average rate of patientspracticing HBP measurement was 27.6% (6). On the other hand, Cuspidi et al. reportedthat 74.7% of Italian treated hypertensive patients were regularly performing HBP (7).The patients practicing HBP measurement were younger and more likely to be male, andhad a higher educational level. The prevalence of HBP measurement also rose with an age.

HBP group showed a significantly higher prevalence of poor BP control in thepresent study. All patients on monotherapy took their drugs in the morning. Among thepatients on the combination therapy, the frequency of the patients who took a twice (ormore) a day regimen was significantly higher in the HBP group than the non-HBP group(62% vs. 41%, p < 0.01). The finding that more patients in the HBP group took theirdrugs in the evening may lead to higher clinic SBP measured during daytime in thisgroup. In the present study, we also found that the number of antihypertensive drugswas significantly greater in the non-HBP group in men, but not women. Concerning thenumber of antihypertensive drugs, we may speculate that obtaining the information onhome BP resulted in the less intensive treatment compared to the treatment based onlyon office BP. However, we are unable to explain the reason why the difference in thenumber of antihypertensive drugs between the HBP and non-HBP groups was observedonly in men.

Despite the increasing recognition on the importance of HBP measurement, only afew studies examined the association between HBP measurement and office BP controlstatus. Staessen et al. compared antihypertensive treatment based on HBP measurementwith office BP measurement (8). The target DBP for both office- and home-based BP

Table 3Reasons for poor office BP control

Non-HBP HBP

White coat effects Unknown 40.6%On the way to target BP 17.6% 18.8%Encouraging lifestyle modification 28.4% 14.8%Resistant HT 16.2% 7.8%BP was high by chance 10.8% 5.5%Strict BP control was hesitated

considering age or complication14.9% 4.7%

Patients refused intensive drug therapy

4.1% 2.3%

Poor compliance with medication 2.7% 0.8%Others 5.4% 4.6%

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230 K. Eto et al.

measurement groups was 80–89 mmHg. The final office, home, and 24-hour ambulatoryBP were higher in the home BP group than in the office BP group. This observation indi-cates that the office BP level of the home BP-based group is higher than that of the officeBP-based group unless the goal BP level of the former group is established to the lowerlevel than that of the latter group. On the other hand, another study (9) showed that patientspracticing HBP measurements had more satisfactory clinic BP control (<140/90 mmHg;49.2% vs. 45.6%, p < 0.01). Halme et al. sought to clarify whether consecutive intermit-tent HBP measurement lead to better control of hypertension, as opposed to conventionalprimary care treatment during a six-month follow-up period. As a result, systolic andpulse pressure reduction was significantly greater in the self-monitoring group (10). Takentogether, the influence of HBP measurements on office BP control in hypertensivepatients is controversial.

HBP measurements constitute an important tool for detecting white-coat hypertension.The prognostic significance of white-coat hytertension (WCH) has been investigated insome event-based cohort (11–14) and interventional studies (15). These reports showedthat individuals with WCH have a risk of major cardiovascular events apparently com-parable with that of clinically normotensive subjects and markedly less than that of sub-jects with elevated daytime BP. Recently, however, Verdecchia et al. analyzedindividual data from four prospective cohort studies from the United States, Italy, andJapan using comparable methodology for 24-hour noninvasive ambulatory blood pres-sure monitoring (ABPM; 16). In their analysis, the adjusted hazard ratio for stroke wasincreased to 1.15 in the WCH group (p = 0.06) and 2.01 in the ambulatory hypertensiongroup (p = 0.001) compared with the normotensive group. After the sixth year offollow-up, the incidence of stroke tended to increase in the WCH group, and the corre-sponding hazard curve crossed that of the ambulatory hypertension group by the ninthyear of follow-up. From these results, they concluded that WCH might not be a benigncondition for stroke in the long term.? If WCH has a comparable risk for stroke toambulatory hypertension in long term, we should make an effort to control both HBPand office BP levels.

The major limitation of this study was the lack of home BP data. Patients in the HBPgroup showed us home BP data; however, we have not determined how to record themand use for the analysis. Thus, we are unable to systematically analyze their home BP val-ues. The diagnosis of the white-coat effect was also made based not on the given criterionof home BP but on the doctors’ decision. It is obvious that HBP measurement is a usefultool for hypertension management for all those patients who are sufficiently motivated totake part in the treatment of their high BP. However, considering the lack of recommenda-tion on the goal home BP, it may be difficult to judge one's home BP as satisfactory. Untilthe goal home BP is clearly indicated, we should make an effort to obtain goal BP basedon office BP. The Hypertension Objective treatment based on Measurement by ElectricalDevices of Blood Pressure (HOMED-BP) study is a large-scale intervention trial to deter-mine both optimal target BP on the basis of self-measured BP at home and optimal initialantihypertensive medication (17). We hope that the results of this study will provideimportant information on the target BP levels based on home BP.

In conclusion, HBP measurement may possibly lead to less strict control of office BP.We have to wait for the accumulation of evidence leading the recommendations on thegoal home and office BP and the strategy to manage the patients with white-coat effect.Until these recommendations are available, we have to carefully follow the patients withwhite-coat effect monitoring not only home and office BP levels but also the presence orprogression of target organ damages.

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HBP Measurement and Office BP Control 231

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