Spatial Dependence of Body Mass Index: Geneva, Switzerland

Urban health (UH) is an emerging field, which explores the effect of urban environment and urbanization on health. Evidence suggests that urban environment can either positively influence health behaviors or be a health stressor. One key approach in UH is the use of georeferenced data and geographic information system (GIS). Mapping disease prevalence and trends provide insight into disease mechanisms and etiologies. An important limitation of GIS is that data sets have likely been collected separately by different agencies, often over different time periods.The Canton of Geneva deviates from this limitation as it has been collecting geographic and health-related information continuously since 1998 through the Unit of Population Epidemiology (UEP) of the Geneva University Hospitals and its Bus Santé study. Combining health-related data from the Bus Santé study and GIS, using Local Indicators of Spatial Association (LISA), the investigators detected significant spatial dependance with respect to BMI. The results clearly indicate that BMI levels are not distributed at random in the Canton of Geneva. Moreover, performing preliminary exploratory analyses on blood pressure, investigators have identified cluster of individuals with higher blood pressure than the average, lifting up possible influences of environmental/urban factors (e.g., sidewalks, traffic, socioeconomic status).