Bone health of the Ovahimba people of north-western Namibia in the context of urbanization and a change of the sociocultural environment.

The prevalence of osteoporosis in Sub-Saharan African (SSA) countries is low, however, as urbanization takes root, it is predicted that bone health will decrease dramatically. The bone health of the semi-nomadic Ovahimba people of Namibia was investigated in the context of urbanization and changes of the sociocultural environment. Furthermore, data on bone health in SSA countries is scarce; there exists no ethnic-specific reference group for people of black origin. Included in the study were 98 urban and rural living Ovahimba people. Quantitative ultrasound was performed, sunrise/sunset saliva cortisol concentrations was measured and a questionnaire was conducted. There was no significant difference in the QUS parameters, however, after adjustment for confounders, SOS and SI differed significantly. The saliva cortisol concentrations differed significantly. After adjustment for confounders, saliva cortisol was significantly negatively correlated to SOS (r= -0.27, p = 0.021) giving an indication for an association between cortisol concentration and QUS parameters. The urban group furthermore showed a nutritional transition. Even though the bone health of the Ovahimba is very good, first signs of the adverse effects of urbanization were detected. Beside changes of lifestyle, this may be attributed to an increased cortisol exposure of the Ovahimba people living in an urban environment due to an increased psychosocial stress.

Alterations of cortisol homeostasis may link changes of the sociocultural environment to an increased diabetes and metabolic risk in developing countries: a prospective diagnostic study performed in cooperation with the Ovahimba people of the Kunene region/northwestern Namibia.

CONTEXT: Diabetes mellitus is increasingly affecting Africa. OBJECTIVE: Urbanization of the Ovahimba people in Namibia is associated with an increased prevalence of disorders of glucose metabolism, and may thus be attributed to changes of cortisol homeostasis. DESIGN: A prospective, cross-sectional, diagnostic study was applied. SETTING: The study was conducted in the field. Location of the Diabetes Epidemic: Africa and Namibia. PARTICIPANTS: Ovahimba people: group 1 "urban" n = 60, 42 females, 46.3 ± 11.3 years (town); group 2 "rural" n = 63, 44 females, 51.1 ± 12.0 years (seminomadic). INTERVENTIONS: oGTT, sunrise and sunset saliva cortisol, metabolic parameters, questionnaire. MAIN OUTCOME MEASURE: The prevalence of disorders of glucose metabolism (DM, IGT, IFT). RESULTS: The prevalence of disorders of glucose metabolism differed significantly: urban group n = 17(28.3%) vs rural group n = 8(12.7%) (P = 0.04). The saliva cortisol concentrations also differed significantly: sunrise 0.34 ± 0.18 vs 0.12 ± 0.15 µg/dL, sunset 0.18 ± 0.20 vs 0.07 ± 0.09 µg/dL, area under the curve 6.16 ± 3.48 vs 2.28 ± 2.56 µg/dL * 24 h (all P < 0.001). Further metabolic parameters were unfavorably changed in the urban group: hip circumference (P < 0.001), waist circumference (P < 0.001), body mass index (P = 0.014), systolic BP at rest (P < 0.001), diastolic BP at rest (P = 0.002), systolic BP after exercise (P < 0.001), heart rate after exercise (P = 0.007), fasting glucose (P < 0.001), 2-h-glucose by OGTT (P = 0.002), triglycerides (P = 0.04), HDL-cholesterol (P = 0.014), prevalence of the metabolic syndrome (P < 0.001). Physical activity was higher in the rural group, and intake of fast food and sweets were higher in the urban group. CONCLUSIONS: Urbanization of the Ovahimba people is associated with an increasing prevalence of disorders of glucose metabolism and other unfavorable metabolic parameters. Besides changes of lifestyle, this may be attributed to an increased cortisol exposure of the Ovahimba people living in an urban environment.