Biological variations associated with change in lifestyle among the pastoral and nomadic tribes of East Africa

Abstract

The values of a number of anthropometric, cardiovascular and biochemical variables have been compared between tribal and non-tribal Samburu. Significant differences between the two groups were found for ponderal index, supra-iliac and mid-calf skinfold thicknesses, pulse rate and both systolic and diastolic blood pressures. Similar analyses were performed on samples from tribal and non-tribal Maasai; here significant differences were found for ponderal index, height, biceps skinfold thickness, pulse rate and systolic blood pressure. No significant differences were found in serum cholesterol or serum triglyceride for either the Samburu or the Maasai. Greater variability of the skinfold measurements was found in the non-tribal Samburu than in the tribal group; this effect was less marked in the Maasai. A principal component analysis and three discriminant function analyses were performed on the Samburu data. These analyses showed that the most marked difference between the tribal and non-tribal groups was in their blood pressure levels, the non-tribal sample having significantly higher mean values than the tribal members. Possible causes for the observed differences between tribal and non-tribal groups are discussed, and the findings are contrasted with those of an earlier study, in which significant differences in cholesterol but not in blood pressure were found between samples of rural and urban Maasai. This leads to the tentative hypothesis that blood pressure is affected immediately by the change in environment, whereas the effect on cholesterol levels is a longer-term one.