Estimating subnational prevalence trends of cardiovascular disease risk factors, tobacco use, overweight, and obesity in East Africa using adaptive kernel density estimation for survey data

Background: Cardiovascular disease (CVD) is increasing in Sub-Saharan Africa (SSA). Overweight/obesity and tobacco use are modifiable CVD risk factors, however literature about the spatiotemporal dynamics of these risk factors in the region at subnational or local scales is lacking. We describe the spatiotemporal trends of overweight/obesity and tobacco use at subnational and subpopulation levels over a 13-year period (2003 to 2016) in five East African nations. Methods: Cross-sectional, nationally representative Demographic and Health Surveys (DHS) were used to explore the subnational spatiotemporal patterns of tobacco use and overweight/obesity in Burundi, Kenya, Rwanda, Tanzania, and Uganda, five East African Community (EAC) nations with unique cultural landscapes influencing CVD risk factors. Adaptive kernel density estimation and logistic regression were used to determine the spatial distribution and change over time of CVD risk factors on a subnational and subpopulation (rural/urban) scale. Results: Subnational and subpopulation analysis shows that regional and national level analysis masks important trends in CVD risk factor prevalence. Overweight/obesity and tobacco use trends were not similar: overweight/obesity prevalence increased across most nations included in the study and the inverse was true for tobacco use prevalence. Urban populations in each nation were more likely to be overweight/obese than rural populations, although the magnitude of difference varied widely between nations. Although the prevalence of overweight/obesity increased over time in both urban and rural populations, spatial analysis revealed that the rate of change was not equal across all urban and rural areas. Rural populations were more likely to use tobacco than urban populations, though the likelihood of use varied substantially between nations. Additionally, spatial analysis showed that tobacco use was not distributed evenly over space: tobacco use increased in and around major cities and urban centers but declined in rural areas. Conclusions: We highlight the importance of de-homogenizing research about CVD risk factors in SSA. Studies of national prevalence trends for CVD risk factors mask important information about subpopulation and place-specific behavior and drivers of risk factor prevalence. Spatially explicit studies are vital to understand local drivers of risk factor trends which can in turn inform policy and public health intervention.