Greenspace inversely associated with the risk of Alzheimer’s disease in the mid-Atlantic United States
Alzheimer’s disease (AD) is a chronic neurodegenerative disease and the most common form of dementia in older populations. Treatment of AD symptoms is very challenging and expensive. Appropriate diet, and mental and physical activity may delay or reduce the occurrence of AD. It is unknown whether environmental factors offer potentially protective effects against the development of AD. We explored the possible beneficial effects of greenspace (trees and herbaceous cover) and blue space (water area) on AD incidence in the mid-Atlantic US. Data for AD diagnoses during 2011-2013 were obtained from Medicare records for 2999 ZIP codes. The percentages of land cover classes in each ZIP code were calculated based on high-resolution land cover imagery. Associations between the risk of developing AD and greenspace, blue space and other variables were examined using zero-inflated Poisson models. AD incidence was negatively associated with greenspace (for a greenspace increase of 10%, risk ratio (RR) =0.91, 95% confidence interval (CI): 0.89-0.94) and blue space (for a water area increase of 10%, RR =0.85, 95% CI: 0.81-0.89), but a positive association was found with the concentration of PM2.5 (RR=1.03, 95% CI: 1.02-1.05 for an increase in PM2.5 of 1 µg/m3). The inverse relationship between green and blue spaces and the risk of AD held across season, gender and race. Our results suggest that green and blue spaces may have protective effects for AD, although potential mechanisms are unclear and require further investigation.