Predisposing factors of hypertension in black males in the process of urbanisation

Abstract

Social and cultural disruption resulting from urbanisation is a major cause of chronic levels of stress all over the world, especially in developing countries like South Africa. South Africa's black population (77 .2 percent of the total population) is in a major process of ubanisation. It is estimated that urban growth and population increases will double or triple the number of urban residents in the next ten years. Urbanisation is linked to a decrease in the health status of various pop_ulation groups, especially regarding black people. In order to evaluate the possible decrease in cardiovascular health due to the exposure to factors associated with urbanisation, a group of 348 black Setswana speaking men was used in this study. The group consisted of 127 men from monocultural rural environments and 221 men from multicultural urban environments. These groups were further subdivided according to their age as well as their hypertensive and norrnotensive state. The cardiovascular parameters during rest and while challenging the cardiovascular system were registered. Applying 50% of the maximal tractive power of the subject on an isometric hand dynamometer challenged the subject's cardiovascular system. The whole pulse wave was recorded by the Finapres apparatus and the cardiovascular parameters were calculated by making use of the "Modelflow" software program. An urbanisation effect was apparent with the cardiovascular parameters during rest and while challenging the cardiovascular system, although the systolic and diastolic reactivity values showed mixed results. The decrease in cardiovascular health amongst the urbanised groups pointed to the possibility of an underlying peripheral vascular mechanism. The changes in the cardiovascular parameters during urbanisation show the same pattern as the changes observed between the hypertensives and normotensives. The urbanised groups showed an increased systolic blood pressure due to a decreased arterial compliance, and an increased diastolic blood pressure due to an increased total peripheral resistance, resulting in a decreased stroke volume and cardiac output when compared to the rural and normotensive groups. A possible interaction between age and the factors associated with urbanisation was found leading to the decreased arterial compliance observed in the older urbanised group. The conclusion, apart from the above mentioned findings, is that the factors associated with urbanisation has a deleterious effect on the cardiovascular health of black Setswana speaking males in the North West province. This is the first study to determine an interaction between urbanisation and age on arterial compliance.