Correlates of blood pressure in an urban Zimbabwean population and comparison to other populations of African origin

Abstract

We have evaluated the relationship between systolic blood pressure (SBP) and age, body mass index (BMI), waist circumference, sodium to potassium ratio (Na/K), and tobacco use in an urban African population. We conducted a random, population-based, cross-sectional survey of people 25 years and older in Marondera, Zimbabwe, with over-sampling in older age groups (n = 775), using a method comparable to that used in International Collaborative Study on Hypertension in Blacks (ICSHIB). The age-adjusted prevalences of hypertension in Marondera (SBP >140/DBP >90/antihypertensive medication) were 30% for women and 21% for men. The average BMI was 26.3 kg/m2 for women and 21.4 kg/m2 for men. The prevalence of hypertension had a steep association with age and in women ranged from 15% (25–34 years) to 63% (55 years and over) and in men from 9% to 47%. No tobacco use in women and greater Keywords: hypertension; obesity; Africa; black; Zimbabwe Introduction Many recent studies have reported high levels of hypertension in urban southern African populations.1–7 The prevalence of hypertension in an urban Zulu population in South Africa was 25% using World Health Organisation (WHO) criteria systolic blood pressure (SBP) >160 and/or diastolic blood pressure (DBP) >95 mm Hg for people between 30 and 65 years of age with slight increases and decreases in the criterion for younger and older people respectively.1 In an urban black population in Johannesburg, South Africa, the mean SBP in men and women aged 40–49 was 140 and 147 mm Hg, respectively, and was still higher in older age groups.2 Among women of child bearing age in a mining town in Zimbabwe, the prevalence of hypertension (SBP >160 or DBP >95 mm Hg or use of hypertensive medications) was 15%3 and the average SBP in urban Zimbabwean women, aged 40 and Correspondence: Dr Jacob Mufunda, Department of Physiology, University of Zimbabwe, P.O. Box MP167 Harare, Zimbabwe Received 30 July 1998; revised 21 April 1999; accepted 21 May 1999 Na/K ratio in spot urines in men were significantly associated with an increased SBP. In both men and women the levels of hypertension and SBP were strongly positively associated with BMI, although the relationship appeared to plateau in women with a BMI greater than >25 kg/m2 . At a given BMI, men and women had similar SBPs and prevalences of hypertension. There is a very high prevalence of hypertension among urban Zimbabweans, particularly among women. Under the assumption the studies are comparable, the prevalence of hypertension in Zimbabwean women (41%) and men (26%) after age adjustment to the ICSHIB populations, appeared higher than almost all of the ICSHIB populations, including those with higher average body mass indexes.