Prevalence of hypertension and associated cardiovascular risk factors in an urban slum in Nairobi, Kenya: A population-based survey

Abstract

Background: Urbanisation has been described as a key driver of the evolving non-communicable disease (NCD) epidemic. In Africa, hypertension is the commonest cardiovascular problem. We determined the prevalence and risk factor correlates of hypertension in the largest Nairobi slum. Methods: In 2010 we conducted a population-based household survey in Kibera, a large informal settlement in Nairobi City; utilising cluster sampling with probability proportional to size. Households were selected using a random walk method. The WHO instrument for stepwise surveillance (STEPS) of chronic disease risk factors was administered by trained medical assistants, who also recorded blood pressure (BP) and anthropometric measures. BP was recorded using a mercury sphygmomanometer utilising the American Heart Association guidelines. Hypertension was defined as per the 7th Report of the Joint National Committee or use of prescribed antihypertensive medication. Those with hypertension or with random capillary blood sugar (RCBS) >11.1 mmol/l had an 8 hours fasting venous blood sugar sample drawn. Age standardised prevalence was computed and multivariate analysis to assess associations. Results: We screened 2200 and enrolled 2061 adults; 50.9% were males; mean age was 33.4 years and 87% had primary level education. The age-standardised prevalence of hypertension (95% CI) was 22.8% (20.7, 24.9). 20% (53/258) were aware of their hypertensive status; 59.3% had pre-hypertension; 80% reported high levels of physical activity and 52% were classified as harmful alcohol drinkers; 10% were current smokers and 5% had diabetes. Majority of males had normal BMI and waist circumference, whereas a third of females were obese or overweight and 40% had central obesity. Older age, higher general and central obesity were independently associated with hypertension and higher SBP and DBP readings. Conclusions: Our findings of high prevalence of hypertension, in association with excess body weight in this poor urban slum community, point to the need for greater awareness and implementation of primary preventive strategies. Keywords: Hypertension prevalence, Urban health, Poverty areas, Africa South of the Sahara, Non-communicable diseases