A longitudinal analysis of the association between long-term exposure to air pollution and cognitive function among adults aged 45 and over in China

Abstract

Objectives Evidence suggests long-term exposure to fine particulate matter air pollution (PM2.5) is associated with a higher risk of cognitive impairment especially among older adults. This study examines the relationship between PM2.5 exposure and cognitive function in China’s ageing population. Method We used longitudinal data from the China Health and Retirement Longitudinal Study (2011-2015) linked with historical PM2.5 concentrations (2000-2015) from remotely sensed satellite data. Growth curve models were applied to estimate associations between PM2.5 exposure (measured in intensity, duration, and a joint variable of intensity with duration for cumulative exposure) and cognitive function. Results Relative to the lowest exposure group, exposure in the second group of PM2.5 intensity (35-50 μg/m3) is associated with poorer cognitive function, but higher levels of PM2.5 appear to be associated with better cognitive function, indicating a U-shaped association. Similar patterns are seen for fully adjusted models of PM2.5 duration: the second group (13-60 months) is associated with worse cognitive function than the first group (0-12 months), but coefficients are non-significant in longer duration groups. Joint analysis of PM2.5 intensity with duration suggests that duration may play a more detrimental role in cognitive function than intensity. However, we do not find a statistically significant association between PM2.5 exposure and rate of cognitive decline. Discussion Our findings are mixed and suggest that some categories of higher and longer exposure to PM2.5 are associated with poorer cognitive function, while that exposures do not hasten cognitive decline. However, more work is necessary to disentangle PM2.5 exposure from individuals’ background characteristics, particularly those jointly associated with cognitive function and urban living.