Neighborhood Sidewalk Environment and Incidence of Dementia in Older Japanese Adults

Sidewalks are indispensable environmental resources for daily life in that they encourage physical activity. However, the proportion of sidewalk coverage is low even in developed countries. We examined the association between neighborhood sidewalk environment and dementia in Japan. We conducted a 3-year follow-up (2010-2013) among participants in the Japan Gerontological Evaluation Study, a population-based cohort study of community-dwelling older adults. We ascertained the incidence of dementia for 76,053 participants from the public long-term care insurance system. We calculated sidewalk coverage (sidewalk area as a percentage of road area) within 436 residential neighborhood units using geographic information systems. Multilevel survival models were used to estimate hazard ratios for the incidence of dementia. During follow-up, 5,310 dementia cases were found. In urban areas, compared with the lowest quartile of sidewalk coverage, the hazard ratio was 0.42 (95% confidence interval: 0.33, 0.54) for the highest quartile, adjusting for individual covariates. After successive adjustments for other neighborhood factors (land slope; numbers of hospitals, grocery stores, parks, railway stations, and bus stops; educational level; and unemployment rate), the hazard ratio remained statistically significant (hazard ratio = 0.71, 95% confidence interval: 0.54, 0.92). Living in a neighborhood with a high level of sidewalk installation was associated with low dementia incidence in urban areas.