Contribution of the physical environment to socioeconomic gradients in walking in the Whitehall II study.

Socioeconomic gradients in walking are well documented but the underlying reasons remain unclear. We examined the contribution of objective measures of the physical environment at residence to socioeconomic gradients in walking in 3363 participants (50-74years) from the Whitehall II study (2002-2004). Individual-level socioeconomic position was measured as most recent employment grade. The contribution of multiple measures of the physical environment to socioeconomic position gradients in self-reported log transformed minutes walking/week was examined by linear regression. Objective measures of the physical environment contributed only to a small extent to socioeconomic gradients in walking in middle-aged and older adults living in Greater London, UK. Of these, only the number of killed and seriously injured road traffic casualties per km of road was predictive of walking. More walking in areas with high rates of road traffic casualties per km of road may signal an effect not of injury risk but of more central locations with multiple destinations within short distances ('compact neighbourhoods'). This has potential implications for urban planning to promote physical activity.