Is There an Association between Sleeping Patterns and Other Environmental Factors with Obesity and Blood Pressure in an Urban African Population?

Beyond changing dietary patterns, there is a paucity of data to fully explain the high prevalence of obesity and hypertension in urban African populations. The aim of this study was to determine whether other environmental factors (including sleep duration, smoking and physical activity) are related to body anthropometry and blood pressure (BP). Data were collected on 1311 subjects, attending two primary health care clinics in Soweto, South Africa. Questionnaires were used to obtain data on education, employment, exercise, smoking and sleep duration. Anthropometric and BP measurements were taken. Subjects comprised 862 women (mean age 41 +/- 16 years and mean BMI 29.9 +/- 9.2 kg/m(2)) and 449 men (38 +/- 14 years and 24.8 +/- 8.3 kg/m(2)). In females, ANOVA showed that former smokers had a higher BMI (p<0.001) than current smokers, while exposure to second hand smoking was associated with a lower BMI (p<0.001) in both genders. Regression analyses demonstrated that longer sleep duration was associated with a lower BMI (p<0.05) in older females only, and not in males, whilst in males napping during the day for >30 minutes was related to a lower BMI (beta = -0.04, p<0.01) and waist circumference (beta = -0.03, p<0.001). Within males, napping for >30 minutes/day was related to lower systolic (beta = -0.02, p<0.05) and lower diastolic BP (beta = -0.02, p = 0.05). Longer night time sleep duration was associated with higher diastolic (beta = 0.005, p<0.01) and systolic BP (beta = 0.003, p<0.05) in females. No health benefits were noted for physical activity. These data suggest that environmental factors rarely collected in African populations are related, in gender-specific ways, to body anthropometry and blood pressure. Further research is required to fully elucidate these associations and how they might be translated into public health programs to combat high levels of obesity and hypertension.