Abstract
Sub-Saharan Africa is experiencing rapid urban growth. Cities enable greater access to health services and improved water and sanitation infrastructure, leading to some improvements in health. However, urban settings may also be associated with more sedentary, stressful lifestyles and consumption of less nutritious food. C-reactive protein (CRP) is a measure of chronic inflammation predictive of cardiovascular disease, and high body mass index (BMI), a ratio of weight to height, indicates overweight or obesity and is associated with an increased risk of many chronic diseases. To explore the association between urbanicity and these two markers, we overlaid data from the 2010 Tanzania Demographic and Health Survey (DHS) with a satellite-derived measure of built environment. Linear regression models were constructed for the outcomes of BMI and CRP, by 1) administratively defined urban/rural categorization from the DHS, 2) satellite derived built environment, and 3) built environment stratified by urban/rural. A total of 2,212 women were included; 23% had elevated CRP, 21% were overweight or obese. A third (33%) lived in a highly built up area and 29% lived in an area classified as urban. A strong positive association between both CRP and BMI and built environment was detected; log CRP increased 0.43 in the highest built up areas compared to not built up (p<0.05); log BMI increased 0.02 in the most built up areas compared to not built up (p<0.05). However, comparing urban to rural category was only significant in unadjusted models. Models stratified by urban/rural category highlight that the variation in CRP and BMI by built environment is mainly driven by rural areas; within urban areas there is less variation. Our findings highlight the potential negative effects of urbanicity on chronic disease markers, with potentially more change detected for those transitioning from rural to urban lifestyles. Satellite-derived urbanicity measures are reproducible and provide more nuanced understanding of effects of built environment on health.
Highlights
Urban environments, as well as the process of urbanization, are believed to have both positive and negative effects on health
We explored the association between Global Human Settlement Layer (GHSL) built environment and C-reactive protein (CRP) and body mass index (BMI) stratified by urban or rural classification
Because urbanization is associated with wealth, and the Demographic and Health Surveys (DHS) wealth measure is associated with urban residence [31], as it includes in its measure commodities and services more likely to be found in urban areas–we explored interactions between wealth and urban/rural but these were not statistically significant
Summary
As well as the process of urbanization, are believed to have both positive and negative effects on health. Residents of urban environments often have greater access to health care and social services, access may differ by city size [2] and may not be distributed among all residents. Urban environments tend to offer greater access to education and increased job opportunities, both of which can improve health. While urban life offers many benefits, some argue that urban spaces may create negative psychosocial factors due to experiences of social fragmentation, overcrowding, and crime prevalent in some cities [7]. A study in Burkina Faso found high rates of major depressive episodes among the urban poor due to chronic health problems and poor standard of living [8]
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