Prevalence, associated factors and relationship between prehypertension and hypertension: a study of two ethnic African populations in Northern Nigeria

To determine the prevalence and relationship between prehypertension and hypertension, we studied 782 ethnic Hausa and Fulanis (men, 409; women, 373) aged 38.9±13.9 years recruited by multistage cluster sampling. Demographic, anthropometry, metabolic and JNC VII-based blood pressure categories were obtained and analysed using univariate and multivariate models. The prevalence rates of prehypertension and hypertension were 58.7% (men 59.2%, women 58.2%) and 24.8% (men 25.9%, women 23.6%), respectively. Only 16.5% of the population had JNC VII defined optimum blood pressure. Compared to hypertension, prehypertension had earlier onset (second versus third decade) and peak (fourth versus fifth decade) of life. The peak and trough prevalence of hypertension and prehypertension, respectively were observed in the 5th decade of life. Obesity, abnormalities of glucose metabolism and insulin resistance were the major factors associated with prehypertension and hypertension. Multivariate analysis identified obesity and impaired glucose tolerance as independent predictors of hypertension. Of those with hypertension, 13.9% were aware of their high blood pressure status of which 85.7% were commenced on treatment and 12.5% achieved blood pressure control. Overall, 1.5% of the study population had blood pressure <140/90 mm Hg. It is concluded that less than 20% of people of Hausa and Fulani ethnicities had optimum blood pressure. These are predominantly in their second decade of life suggesting that rise in blood pressure begins early in this population. The fifth decade of life may represent a period of transition from prehypertension to hypertension.