An epidemiological study of hypertension and its determinants in a population in transition: the THUSA study

Many black persons in South Africa have been subjected to urbanisation and urbanisation has led to a significant increase in diseases of lifestyle. The determinants of hypertension in a population in transition have not been well-defined and there is a pressing need for observational epidemiological studies as well as randomised-controlled trials in populations from Africa. The aim of this study was to investigate the association between blood pressure and factors known to contribute to hypertension.

The study sample consisted mainly of Setswana speaking people, divided into different levels (strata) of urbanisation, namely stratum 1 (rural) to stratum 5 (urbanized). A total of 1821 black subjects, which included 1040 woman, were recruited and randomly selected from 37 sites from the four geographical quarters of the North West Province of South Africa. The following questionnaires were used: demographic, anthropometric, quantitative food frequency, physical activity and scales to measure psychosocial variables. Biochemical analysis (standardised methods) were done on the serum and plasma of the subjects and the blood pressure was measured with a sphygmomanometer.

Of the total sample, 22.8% of the subjects had systolic and 20.7% diastolic blood pressures above 140/90 mm Hg. Males and females from stratum 3 showed the highest rate of hypertension (32.9% systolic and 25.1% diastolic) and stratum 5 the lowest. Blood pressure correlated positively with age, level of urbanisation, WHR (waist:hip ratio) and smoking. In the woman the diastolic blood pressure correlated the best with body mass index (BMI), serum triglycerides, total serum cholesterol, low-density lipoprotein (LDL) cholesterol and s-GGT. Coping strategies, experience of social support, cultural aspects and affect balance are related to blood pressure, especially in the case of women.

It seems that factors associated with urbanisation are related to the manifestation of hypertension in black people of the North West Province, given the highest mean blood pressure in people living in informal settlements, where most newcomers to the urban areas live. Journal of Human Hypertension (2000) 14, 779-787