Urban Densification and Physical Activity Change: A 12-year Longitudinal Study of Australian Adults.

Urbanization, a major force driving changes in neighborhood environments, may affect residents' health by influencing their daily activity levels. We examined associations of population density changes in urban areas with adults' physical activity changes over 12 years using the Australian Diabetes, Obesity and Lifestyle study (1999-2012). The analytical sample contained 2,354 participants, who stayed at the same residential address throughout the study period in metropolitan and regional cities (42 study areas). Census-based population density measures were calculated for 1-km radius buffers around their homes. Population density change was estimated using linear growth models. Two-level linear regression models assessed associations between changes in population density and changes in self-reported walking and physical activity durations. The average population density change was 0.8% [range: -4.1 to 7.8] per year relative to baseline density. After adjusting for confounders, each 1% annual population density increase was associated with 8.5 (95% CI: 0.6, 16.4) and 19.0 (95% CI: 3.7, 34.4) minutes/week increases in walking and physical activity, respectively, over the 12 years. Increasing population density through urban planning policies of accommodating population growth within the existing urban boundary, rather than expanding city boundaries, could assist in promoting physical activity at the population level.