Improvement of blood pressure control in a hypertension clinic: a 10-year follow-up study

Abstract

The objective of the study was to assess whether the publication of new guidelines, such as JNC VI 1997 and WHO/ISH 1999, and the development of new antihypertensive drugs have improved blood pressure (BP) control. A total of 150 patients (age 29–88, mean 66±11 years in 2001) who were followed at our hypertension clinic during 1991–2001 were retrospectively investigated. We compared the clinical characteristics of the patients in 2001 to those in 1991 and 1996, using the averaged BP determined at two occasions each year for our analysis. The average BP decreased during the 10 years between 1991 and 2001. When good BP control was defined as <140/90 mmHg, the rate of patients with good BP control increased from 31% in 1991 to 43% in 1996, and to 57% in 2001 (P<0.001 vs 1991). Both younger (64 years) and older (65 years) patients showed similar improvement during these 10 years. In 2001, satisfactory BP control (<130/85 mmHg) was achieved in 24% of younger patients, which was significantly higher than the achievement in 1991 (10%, P=0.02). This improvement occurred at the same time as an increase in the prescription of Ca antagonists and angiotensin II antagonist. The patients with improved BP control during these 10 years (n=50) showed lower body mass index (BMI) and serum total cholesterol levels in 2001 compared to persistently uncontrolled patients (n=54). Furthermore, the change in BMI during these 10 years was significantly less in the patients with improved BP control than in the persistently uncontrolled patients. In conclusion, BP control improved in the 10 years studied, and it seems to be attributable to the more frequent use of the newer drugs such as angiotensin II antagonists and Ca antagonists, to lifestyle modification and also to the growth in awareness of the importance of strict BP control.

Introduction

Hypertension is a major risk factor for the development of stroke, coronary heart disease and renal failure.1,2 A number of randomized controlled trials have shown that antihypertensive treatment significantly reduces cardiovascular mortality and morbidity, and there is evidence that the benefit achieved is related to the extent to which blood pressure (BP) is lowered.3,4,5,6 Based on the findings obtained from the large-scale clinical trials, recent guidelines for the management of hypertension, such as JNC VI 1997 and WHO/ISH 1999, recommend strict BP control.2,7 The development of new antihypertensive drugs, including angiotensin II antagonists, may have a beneficial influence on the management of hypertension. Thus, the aim of the present study was to assess whether BP control improved during the 10 years between 1991 and 2001 and, if there was improvement, to determine what factors influenced the improved control.

Methods

A total of 150 patients who were followed at the hypertension outpatient clinic of the Kyushu University hospital during 1991–2001 were investigated retrospectively. We compared the clinical characteristics of the patients in 2001 to those in 1991 and 1996. We recorded patient sex; age; body mass index (BMI); presence of diabetes mellitus (DM); habitual alcohol intake and amount of smoking, if any; proteinuria, defined as dipstick proteinuria of greater than +1; and antihypertensive regimens followed. DM was defined as fasting plasma glucose >126 mg/dl or plasma glucose at any time 200 mg/dl or HbA1c6.5% or the current use of hypoglycaemic agents. Serum creatinine and total cholesterol were also determined. Left ventricular hypertrophy (LVH) was diagnosed by electrocardiogram using the Sokolow–Lyon criterion (SV1+RV5/RV6>38 mm). Clinic BP was measured in the sitting position by physicians using a mercury sphygmomanometer. The averaged BP determined at two occasions between March and May each year was used for analysis. We have chosen to use BP measurements in spring to exclude the possible influence of seasonal variation of BP on the trend of BP control during 10 years observation period. ‘Good control’ was defined as systolic blood pressure (SBP) of <140 mmHg and diastolic blood pressure (DBP) of <90 mmHg. ‘Satisfactory control’ was defined as SBP of <130 mmHg and DBP of <85 mmHg.

Statistical analysis

All values are expressed as means±s.d. To evaluate the changes in patient characteristics among the years of 1991, 1996 and 2001, we used a one-way ANOVA followed by Fisher's multiple range test. We used Student's t-test to compare the patient profiles between the patients with improved BP control and sustained uncontrolled patients. A χ2 test was also utilized when appropriate. P-values less than 0.05 were considered to be significant.

Results

Patient characteristics are shown in Table 1. The mean age was 66±11 years in 2001, and 51% of the patients were women. The average BP decreased from 144±17/87±10 mmHg in 1991 to 140±14/84±9 mmHg in 1996, and to 137±13/81±9 mmHg in 2001 (P<0.01). BMI and the prevalence of habitual alcohol intake and smoking were not altered during the 10 years. The mean serum total cholesterol level significantly decreased from 212±34 mg/dl in 1996 to 204±35 mg/dl in 2001 (P<0.05). The proportion of patients who were taking antilipaemic agents significantly increased from 11.3% in 1991 to 33.3% in 2001 (P<0.01). The prevalence of patients who received more than two antihypertensive drugs significantly increased from 40.7% in 1991 and 46.7% in 1996 to 58.7% in 2001. The distribution of individual BP level is shown in Figure 1. The prevalence of patients with good BP control significantly increased from 30.7% in 1991 to 56.7% in 2001 (P<0.01). This improvement was mainly attributable to a reduction in the patients whose DBP levels were greater than 90 mmHg. In contrast, the prevalence of patients whose SBP140 mmHg and DBP<90 mmHg did not change during the 10 years. As shown in Figure 2, similar improvement of BP control was found in both younger (64 years) and older (65 years) patients. In 2001, satisfactory BP control (<130/85 mmHg) was achieved in 23.7% of younger patients, which was significantly higher than the proportion of younger patients who achieved such control in 1991 (9.9%, P=0.02). BP level in patients with proteinuria significantly (SBP: P=0.07; DBP: P<0.01) decreased from 146±13/90±6 mmHg in 1991 to 133±15/79±8 mmHg in 2001. BP level in the patients with DM decreased from 153±20/90±13 mmHg in 1991 to 138±10/83±5 mmHg in 2001. Figure 3 demonstrates the trend in the prescription of antihypertensive drugs during the 10 years. Compared to 1991, significant increases in the prescriptions of Ca antagonists and angiotensin II antagonists were observed in 2001.

Table 1 Trends in patient characteristics
Figure 1
figure1

The distribution of individual BP level.

Figure 2
figure2

The trend in BP control.

Figure 3
figure3

The trend in the use of antihypertensive drug.

Among 104 patients who showed poor BP control in 1991, 54 patients continued to be in the poor BP control group in 2001, while another 50 patients joined the good BP control group. A comparison of characteristics between these two groups is presented in Table 2. The patients with improved BP control showed significantly lower BMI and serum total cholesterol levels in 2001 compared to the levels of persistently uncontrolled patients (22.9±3.3 vs 24.4±2.6 kg/m2, P<0.05; 199±38 vs 213±31 mg/dl, P<0.05). In addition, the change in BMI was significantly different between the groups (−0.67±1.98 vs +0.56±1.82 kg/m2, P<0.05). Other characteristics including age, alcohol intake and smoking did not differ significantly between the groups. The prevalence of patients who took antilipaemic agents was not different between the patients with improved BP control and persistently uncontrolled patients (42 vs 32%, P>0.10). The profile of antihypertensive drugs was not different between them.

Table 2 Comparison of the characteristics of patients with improved BP control and persistently uncontrolled patients

Discussion

The major findings of the present study are that the average BP of hypertensive patients decreased and the rate of patients with good BP control (<140/90 mmHg) significantly increased during the 10 years from 1991 to 2001. The proportion of patients with satisfactory BP (<130/85 mmHg) and with good BP in 2001 was 23.3 and 56.7%, respectively. Several surveys have reported that the proportion of patients with controlled BP varied from 2.5 to 48%,8,9,10,11,12,13,14,15,16,17 suggesting that the proportion of patients with controlled BP in the present study may be higher than that seen in previous studies. This improvement of BP control in the present study might be attributable to several factors, such as prescription of a new drug, lifestyle changes, and an improved physicians’ recognition of the importance of strict BP control as proposed by guidelines.2,7 The improvement of BP control over this period has also been reported in the other countries.18,19

Although a direct assessment of the impact of recent guidelines on the treatment of hypertension is difficult to perform, the significant improvements of BP control in 2001, but not that in 1996, compared with 1991 suggest that the guidelines may have had a positive impact on the clinical treatment of hypertension. It is noteworthy that the improvement of BP control was similar in both younger (64 years) and older (65 years) patients. Since the reduction in cardiovascular mortality and morbidity by antihypertensive therapy has also been demonstrated in old hypertensive patients,4,5,6,20 the importance of strict BP control may also be applicable to the elderly hypertensives. In the present study, BP level in patients with proteinuria or DM also decreased during the 10 years. In the MDRD study, more aggressive BP lowering to slow the progression of renal disease was proposed for patients with proteinuria.21 In a study of UKPDS 38, tight BP control in patients with hypertension and type II DM achieved a clinically important reduction in the risk of deaths and complications related to DM.3 In addition, in the HOT trial, intensive lowering of BP (target DBP80 mmHg) was associated with a lower rate of cardiovascular events and death in patients with hypertension and DM.5 Based on these observations, the guidelines emphasized strict BP control, particularly in patients with proteinuria or DM.

Several independent predictors of poor BP control, such as age, alcohol and sodium intakes, and patient lack of awareness about target BP levels have been proposed.14,15,22,23,24,25 In addition, obesity and hypercholesterolaemia have been shown to be associated with poor BP control.14,23,24,26,27 To support this idea, recent trials have shown that the use of nonpharmacological advice has contributed to improved BP control.9,11,13,23,25,26,27,28,29,30,31,32,33,34 In the present study, BMI did not change during the 10 years; however, the patients with improved BP control during this period showed significantly lower BMI than did persistently uncontrolled patients. In addition, the change in BMI was significantly less in the former. In the TOHP study, weight loss and reduction in sodium intake, individually and in combination, were effective in lowering BP.32,33 Similarly, the TONE study has shown that the reduced sodium intake and weight loss constitute a feasible, effective and safe nonpharmacologic therapy for hypertension in older persons.34 Obesity has long been recognized as an important risk factor for a large array of diseases, such as metabolic disorders and cardiovascular disease.35 The association between obesity and hypertension and their relationship to the underlying mechanism of insulin resistance has been well documented.35 Although we have not investigated the dietary habit, the present findings may support the evidence that nonpharmacologic therapy has a significant influence on the long-term improvement of BP control. Indeed, salt intake in Japan, which was traditionally high, has been decreasing in recent years.36

Serum total cholesterol levels decreased during the 10 years, which was associated with the increased prescriptions of antilipaemic agents. Interestingly, the patients with improved BP control during these 10 years showed significantly lower serum total cholesterol levels than did persistently uncontrolled patients. Therefore, our data suggest that the integrative management of the body weight and serum total cholesterol levels may be an important factor in achieving good BP controls. Certain hydroxymethylglutaryl coenzyme A reductase inhibitors have shown to decrease SBP and pulse pressure (PP).37 However, the contribution of these drugs to the improvement of BP control is unclear in the present study.

The improvement of BP control in the present study was associated with the increased prescriptions of new antihypertensive drugs, such as Ca antagonists and angiotensin II antagonists during these 10 years. The improvement of BP control by using Ca antagonists and angiotensin-converting enzyme inhibitors has also been reported in previous studies.28,38 The WHO/ISH guidelines and other studies also emphasize the efficacy of combination therapy.2,5,39,40 As regard to the combination therapy, the prevalence of patients who were taking more than two antihypertensive drugs significantly increased during 10 years in our study. Thus, the prescriptions of new antihypertensive drugs as well as the increased use of combination therapy seemed to associate with the improvement of BP control.

The average SBP as well as DBP of our patients significantly decreased during the 10 years (144± 17 vs 137±13 mmHg, P<0.01; 87±10 vs 81±9 mmHg, P<0.01). Compared to the low frequency of patients with uncontrolled DBP (14%), 40% of the patients failed to achieve SBP of 140 mmHg in 2001. Thus, the insufficient control of SBP is the main determinant of unsatisfactory BP control. DBP has long been regarded as an important predictor of target organ damage in hypertension. Recently, several prospective studies have indicated that SBP and PP are more powerful predictors of the risk of cardiovascular disease than DBP.24,41 The efficacy of antihypertensive treatment in elderly patients with isolated systolic hypertension has also been confirmed in large clinical trials.6,42 Thus, the effort to achieve a goal SBP level is essential for obtaining satisfactory BP control.

In conclusion, the average BP level in 2001 significantly decreased compared with that in 1991, and the proportion of patients with good BP control increased. This improvement of BP control was attributable to the more frequent use of new antihypertensive drugs as well as the greater level of recognition by physicians of the importance of strict BP control. Lifestyle modification such as the control of body weight and fat intake might also contribute to the improvement of BP control.

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Author information

Correspondence to Y Ohta.

Additional information

This study was presented at the 19th Scientific Meeting of the International Society of Hypertension in June 23–27, 2002, Prague, Czech Republic

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Ohta, Y., Tsuchihashi, T., Fujii, K. et al. Improvement of blood pressure control in a hypertension clinic: a 10-year follow-up study. J Hum Hypertens 18, 273–278 (2004). https://doi.org/10.1038/sj.jhh.1001666

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Keywords

  • BP control
  • antihypertensive drugs
  • lifestyle modification
  • body mass index
  • serum total cholesterol level

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