Is the 'rule of halves' in hypertension still valid? - evidence from the Chennai Urban Population Study

Abstract

Aim of the study: The aim of the present study was to assess the applicability of the rule of halves in an urban population in South India. Methods: The Chennai Urban Population Study (CUPS) is an ongoing population based study involving two residential colonies representing a middle and lower socio-economic status in Chennai city. The response rate for the study was 90.1%. Based on a glucose tolerance test (GTT), the study subjects were categorized as having normal glucose tolerance test (NGT), impaired glucose tolerance test (IGT) or diabetes. Blood pressure was measured for all the study subjects and the subjects were classified as hypertensive using the criteria, systolic blood pressure (SBP) > or = 140 mm Hg and/or diastolic blood pressure > or = 90 mmHg and/or known hypertensives and/or treatment with antihypertensive drugs. Controlled hypertension was defined as SBP < 140 mmHg and DBP < 90 mmHg. Results: The overall prevalence of hypertension in this population is 22.1% (279/1262). Of these 279 individuals with hypertension, only 37.3% (104/279) were known hypertensives. Of the 104 known hypertensives, only 52 subjects (50%) were under any kind of antihypertensive therapy. Of these 52 individuals, only 21 (40%) had blood pressure under control. Prevalence of hypertension was higher in subjects with glucose intolerance. Awareness and treatment of hypertension was slightly higher among the diabetic hypertensive subjects. Analysis on the different social classes revealed that the prevalence, awareness and treatment of hypertension to be significantly higher among the middle income group compared to lower income group. Conclusions: The rule of halves is still valid in this urban South Indian population and thus the awareness, treatment and control measures for hypertension are still inadequate in this population.