Cross-sectional surveys on prevalence, treatment and control of hypertension could not satisfactorily distinguish between diastolic hypertension and isolated systolic hypertension because the definition of hypertension included patients under pharmacological treatment. We assessed the situation in the two types of hypertension in general practice in Belgium, based on current blood pressure (BP) measurements and on BP prior to the initiation of drug therapy. Participating physicians enrolled the first 15 at least 55-year-old men visiting the surgery, measured their BP and recorded data on medical history including pretreatment BP, drug utilization, cardiovascular risk factors and target organ damage. Diastolic hypertension was defined as diastolic BP⩾90 mmHg, irrespective of systolic BP, and isolated systolic hypertension as systolic BP⩾140 mmHg and diastolic BP<90 mmHg. Among 3761 evaluable patients, 74% were hypertensive. Among the 1533 hypertensive patients in whom blood pressure was known prior to treatment (n=965) or who were untreated at the study visit (n=568), 1164 had diastolic hypertension and 369 isolated systolic hypertension. The prevalence of antihypertensive treatment was, respectively, 75 and 25% (P<0.001) in these two types of hypertension. The odds of being treated were independently determined by type of hypertension, severity of hypertension and level of risk (P<0.001). BP was controlled in 25% of all patients with diastolic hypertension and in 13% of all patients with isolated systolic hypertension (P<0.001). About half of the treated patients with systolic hypertension were on a diuretic and/or a calcium-channel blocker. In conclusion, isolated systolic hypertension is less frequently treated than diastolic hypertension, overall BP control is poor and actual drug therapy diverges from recommendations based on placebo-controlled intervention trials.
Isolated systolic hypertension is prevalent in the elderly, affecting 5–10% in the sixth decade of life and up to 25% of octogenerians1,2 and is known to be associated with an increased incidence of cardiovascular complications.3 Placebo-controlled clinical trials have convincingly shown that antihypertensive therapy is beneficial in older patients with isolated systolic hypertension.4,5,6 A review of the literature concluded that active treatment reduces the incidence of stroke and of coronary events by, respectively, 30 and 23%.3 Therefore, the most recent guidelines on the management of hypertension recommend pharmacological treatment in elderly with isolated systolic hypertension, in addition to nonpharmacological measures.7,8 Moreover, the 1999 WHO-ISH guidelines8 did not deal separately with hypertension in the elderly nor with isolated systolic hypertension because treatment of these conditions was considered to be at least as effective in reducing cardiovascular risk as the treatment of classical essential hypertension in middle-aged subjects. Little is known, however, on treatment and blood pressure control in elderly with isolated systolic hypertension. The main reason for this lack of knowledge is that in recent surveys on prevalence, treatment and control of blood pressure in various populations,9,10,11,12,13,14,15,16,17,18,19,20 participants were considered to have hypertension when systolic pressure was ⩾140 mmHg, diastolic blood pressure ⩾90 mmHg, or when patients were taking antihypertensive drugs. This definition includes patients with systolic–diastolic hypertension, isolated diastolic hypertension and isolated systolic hypertension. Since a substantial number of patients were under pharmacological treatment and as pretreatment blood pressure was not considered in these cross-sectional surveys, investigators could not satisfactorily distinguish between patients with isolated systolic hypertension and patients with diastolic hypertension. Also studies on treatment and blood pressure control in general practice21,22,23,24 and specialist care25 did not separately report on isolated systolic hypertension and diastolic hypertension. When only untreated and inadequately treated patients were considered in the cross-sectional NHANES III survey,19 isolated systolic hypertension was the most frequent subtype of uncontrolled hypertension in the elderly.
We recently conducted a survey to gain insight into the prevalence, treatment and control of hypertension and into the implementation of the 1999 WHO-ISH guidelines for the management of hypertension in primary care, particularly with regard to risk stratification.26 In the present report, we assess prevalence, treatment and blood pressure control in patients with isolated systolic hypertension in comparison with patients with diastolic hypertension, based on current blood pressure measurements and, in addition, inquiries on blood pressure prior to the initiation of treatment in the treated patients. The survey was performed on older men under medical care by general practitioners in Belgium.
General practitioners throughout Belgium were asked to participate in the project, which was conducted from May to September 2000. After agreement and explanation of the study protocol, physicians had to include the first 15 men age 55 years or older who visited the surgery for any reason except life-threatening diseases. Patients were not selected on the basis of hypertension. Blood pressure and heart rate were measured two times in the sitting position, after 5 min of rest, by use of the validated OMRON HEM-705 CP device,27 which was made available to each participating physician. A questionnaire was filled in, including the reason for the visit, drug utilization, pretreatment blood pressure if applicable, cardiovascular risk factors (smoking, serum cholesterol, family history of premature cardiovascular disease), target organ damage, history of diabetes and associated cardiovascular or renal diseases. Patients were considered to have hypertension when average blood pressure was ≥140 mmHg for systolic pressure or ≥90 mmHg for diastolic pressure, or when they were taking antihypertensive drugs. Hypertensive patients were then classified according to the WHO-ISH proposal for stratification of absolute cardiovascular disease risk, based on level of risk and blood pressure category.8 First, patients were classified into one of three levels of risk, starting at risk level II because the lowest level does not apply to ≥55-year-old men (level II: ⩽one risk factor in addition to being a ≥55-year-old man; level III: ≥two additional risk factors, diabetes and/or target organ damage; level IV: presence of associated clinical conditions, including cardiovascular and renal diseases). Patients were then classified into medium-, high- and very-high-risk categories based on the level of risk and blood pressure.8 For this stratification, blood pressure was the one taken at the study visit in untreated patients or blood pressure prior to the initiation of therapy in treated patients. Untreated hypertension was defined as mild (grade 1) when systolic blood pressure was 140–159 mmHg or diastolic blood pressure 90–99 mmHg, and as moderate (grade 2) when these pressures were 160–179 or 100–109 mmHg, respectively; hypertension was considered severe (grade 3) when systolic blood pressure was ≥180 mmHg or diastolic blood pressure ≥110 mmHg. Isolated systolic hypertension was defined as elevated systolic pressure (≥140 mmHg) and normal diastolic pressure (<90 mmHg) and diastolic hypertension as diastolic blood pressure ≥90 mmHg, irrespective of systolic pressure. To evaluate the control of blood pressure in treated patients, target blood pressure was defined as systolic blood pressure <140 mmHg and diastolic pressure <90 mmHg. Target blood pressure was lower in diabetics (130/85 mmHg) and in patients with renal insufficiency, that is <125/75 mmHg when they had proteinuria of at least 1 g/24 h and <130/80 mmHg in the others.8
The statistical analysis was mainly descriptive and consisted of the calculation of means and standard deviations for quantitative variables, and numbers and percentages for categorical variables. The unpaired Student's t-test was used for intergroup comparisons of quantitative variables and the χ2 test was applied to compare proportions. To estimate the determinants of the odds of being treated stepwise multivariate logistic regression analysis was performed in which type of hypertension (isolated systolic hypertension, diastolic hypertension), hypertension grade (mild, moderate, severe) and level of risk (II, III, IV) were considered as categorical variables that were given the values 0 and 1, and, if applicable, 2; age was included as a quantitative variable. Two-by-two interactions were included in the model containing the significant factors. If they were not significant they were removed from the final model. Tests were performed two-tailed at the 5% level of significance, except for interaction terms of the multivariate logistic regression, which were tested at the 10% level of significance.
A total number of 272 physicians agreed to participate, of whom eight stopped participation and 11 did not return study files. The remaining 253 physicians recruited 3766 men aged ≥55 years, of whom five were excluded from further analysis because blood pressure was not reported on the study file. In total, 74% of these patients had hypertension, of whom 80% were treated with antihypertensive drugs. Based on blood pressure at the study visit in the 568 untreated hypertensives and on knowledge of blood pressure before treatment in 965 patients under antihypertensive therapy (n=1533), 369 patients could be classified as having isolated systolic hypertension and 1164 as having diastolic hypertension; the latter subgroup includes 41 patients with isolated diastolic hypertension (systolic blood pressure <140 mmHg). Isolated systolic hypertension was thus present in 24% of the hypertensive patients, but this percentage amounted to 49% in the untreated patients. Patients with isolated systolic hypertension were on average older than those with diastolic hypertension (Table 1). The percentage of hypertensive patients with isolated systolic hypertension was 19.6% in the 55-to-64-year age category, 25.2% between 65 and 74 years, and 31.4% at age 75 years or over (P<0.001). Untreated systolic blood pressure was higher in the patients with diastolic hypertension.
Prevalence of treatment was three times greater in diastolic hypertension than in isolated systolic hypertension (Table 1). Control of blood pressure in treated patients was better in isolated systolic hypertension than in diastolic hypertension. However, blood pressure control was worse in isolated systolic hypertension than in diastolic hypertension when treated and untreated patients were combined. Diastolic blood pressure was <90 mmHg in 66% of treated diastolic hypertension patients and in 49% of all diastolic hypertension patients. Antihypertensive therapy reduced blood pressure from 162±14/83±3.5 to 140±16/79±9 mmHg in the 93 treated patients with isolated systolic hypertension, and from 172±18/101±10 mmHg to 146±17/85±10 mmHg in the 872 treated patients with diastolic hypertension. In patients with isolated systolic hypertension, 60.4% were on monotherapy, 34.1% were taking two drugs and 5.5% were on three or more drugs; these figures were 52.5, 33.2 and 14.3%, respectively, in patients with diastolic hypertension (P=0.06). Actual drug treatment in patients on monotherapy and in all treated patients in each subgroup is summarized in Table 2.
Risk stratification of hypertensive patients
Information on risk factors, diabetes, target organ damage and associated clinical conditions, required to classify patients according to absolute cardiovascular disease risk, was available in 1316 patients. Among patients with isolated systolic hypertension, 60.4% were at medium risk, 13.9% at high risk and 25.7% at very high risk; these prevalences were, respectively, 31.7, 12.5 and 55.9% in patients with diastolic hypertension (P<0.001). Table 3 compares antihypertensive treatment and blood pressure control for isolated systolic hypertension and diastolic hypertension patients within each category of risk. Prevalence of treatment was always higher in patients with diastolic hypertension than in patients with isolated systolic hypertension.
Table 4 summarizes the results from logistic regression analysis showing that type of hypertension (diastolic hypertension, isolated systolic hypertension), hypertension grade (severe, moderate, mild) and risk level (IV, III, II) contributed independently to the odds of being under pharmacological treatment. None of the two way interactions between the factors retained in the model were significant. The odds for a one-category difference are given in Table 4; the odds for a two-category difference amounted to 12.4 for severe vs mild hypertension and to 4.4 for risk level IV vs risk level II.
A subgroup of particular interest are patients with systolic blood pressure between 140 and 160 mmHg. Table 5 summarizes the data on treatment and blood pressure control in patients with mild hypertension and those with moderate and severe hypertension (two subgroups combined). The prevalence of treatment was particularly low in mild isolated systolic hypertension with risk level II, but was still lower than 50% in patients with mild isolated systolic hypertension and associated clinical conditions (risk level IV).
In the current survey on men at least 55 years old under medical care by general practitioners in Belgium, approximately one-fourth of the hypertensives had isolated systolic hypertension, based on current blood pressure measurements in untreated patients and blood pressure prior to the initiation of therapy in treated patients. The major finding is that only 25% of patients with systolic hypertension were treated with antihypertensive drugs, which is significantly less than the prevalence of 75% in patients with diastolic hypertension. It appears, therefore, that recent recommendations that isolated systolic hypertension should be treated7,8 or even that the same guidelines would apply to isolated systolic hypertension than to hypertension in general8 is not followed in general practice. On the other hand, one should realise that there are no placebo- or nontreatment-controlled outcome trials in patients with uncomplicated mild or grade 1 isolated systolic hypertension. Furthermore, in the Ambulatory Blood Pressure Monitoring side project of the Syst-Eur trial on older patients with isolated systolic hypertension, there was no convincing evidence of benefit of treatment when daytime ambulatory blood pressure was <160 mmHg.28 It may therefore not be surprising that only 10% of patients with systolic blood pressure less than 160 mmHg and at relatively low risk (risk level II) were under pharmacological treatment. However, prevalence of treatment was still less than 50% in patients with mild isolated systolic hypertension and associated clinical conditions, despite the evidence that patients with coronary heart disease, chronic heart failure, and high-risk patients in general,29,30,31,32 would benefit from blood-pressure-lowering drugs.
The SHEP,4 Syst-Eur5 and Syst-China6 trials have convincingly shown that antihypertensive therapy reduces the incidence of cardiovascular complications in patients with moderate-to-severe (grade ≥2) isolated systolic hypertension. Nevertheless, only about half of the patients with systolic blood pressure at or above 160 mmHg were treated, except in the presence of associated clinical conditions, when the prevalence amounted to 78%. Overall, treatment was less frequent in isolated systolic hypertension than in diastolic hypertension, irrespective of severity of hypertension or category of risk. This was clearly shown by logistic regression analysis that revealed that the odds of being treated were independently determined by the type of hypertension, hypertension grade and the level of risk. Diastolic hypertension was treated in at least 80% of the patients, except in patients with mild hypertension with risk levels II and III.
As in many previous surveys in the population,9,10,11,12,13,14,15,16,17,18,19,20 in primary care21,22,23,24 and in specalist care,25 a substantial number of treated patients did not reach target blood pressure, leading to an overall poor blood pressure control. In the current study, blood pressure control was somewhat better in treated patients with isolated systolic hypertension than in those with diastolic hypertension, but the lower prevalence of treatment resulted in a worse overall blood pressure control in isolated systolic hypertension. Despite insufficient blood pressure control, 60 and 52% of treated patients with, respectively, isolated systolic hypertension and diastolic hypertension, were still on monotherapy at the study visit. First-line treatment in the outcome trials in isolated systolic hypertension consisted of a diuretic4 or a dihydropyridine calcium-channel blocker.5,6 Despite this evidence and recommendations in recent guidelines,7,8 only half of the patients with isolated systolic hypertension who were still on monotherapy, were taking a drug belonging to one of these classes. Particularly, the use of a diuretic in only 14.5% of these patients is striking; moreover, a diuretic was only taken by 27.5% of the patients on combination therapy. The fact that the choice of drugs did not differ significantly between patients with isolated systolic hypertension and patients with diastolic hypertension indicates that physicians do not seem to consider the type of hypertension when prescribing antihypertensive drugs.
There are several limitations to the present study. Whereas data were all but complete with regard to blood pressure measurement and actual treatment at the study visit, blood pressure before the initiation of treatment was not always known to the physicians who participated in the survey. The choice of a physician is free in Belgium and treatment had often been started by another doctor. It cannot be excluded that the lack of knowledge of pretreatment blood pressure in a number of patients influenced the results to a certain extent. Data on risk factors and target organ damage needed for risk stratification were not always available in this survey in primary care; to safeguard compliance, we did not request the general practitioners to collect these data if not known. The survey was conducted in men. Most studies observed that treatment of hypertension and blood pressure control are, in general, more favourable in women than in men,33 but no data are available on isolated systolic hypertension in women.
We conclude that approximately 25% of older hypertensive men under medical care by general practitioners in Belgium have isolated systolic hypertension; that patients with the latter condition are less frequently treated than patients with diastolic hypertension leading to an overall worse blood pressure control; that recommendations on the initiation of antihypertensive treatment with a diuretic or a calcium-channel blocker in isolated systolic hypertension are inadequately observed, particularly with regard to the diuretic, and that undertreatment is a frequent cause of insufficient blood pressure control. More efforts should be made to propagate and reinforce current guidelines on the management of hypertension, particularly with regard to isolated systolic hypertension.
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We gratefully acknowledge the secretarial assistance of N Ausseloos and the dedicated collaboration of the many general practitioners. The study was supported by a grant from Pfizer, Belgium. RHF is holder of the Professor A Amery Chair in Hypertension Research.
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Cite this article
Fagard, R., Van den Enden, M. Treatment and blood pressure control in isolated systolic hypertension vs diastolic hypertension in primary care. J Hum Hypertens 17, 681–687 (2003). https://doi.org/10.1038/sj.jhh.1001598
- antihypertensive treatment
- blood pressure control
- isolated systolic hypertension
- primary care
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