Fine Particulate Matter Air Pollution and Cognitive Function in Older Age: Evidence from the Irish Longitudinal Study on Ageing (Tilda)

Abstract

With rapid population ageing worldwide, the number of people with dementia is projected to increase from over 55 million in 2019 to more than 139 million in 2050. Preventing or delaying onset is a global public health priority, as cognitive impairment and dementia comes at a considerable personal and societal cost. Air pollution can increase neurodegeneration through processes including vascular damage, increased systemic inflammation, as well as direct neuronal damage. In this paper, we used data from the Irish Longitudinal Study on Ageing (TILDA) to investigate the relationship between exposure to fine particulate matter (PM2.5) air pollution (proxied by annual average PM2.5 concentrations measured at the residential address of survey respondents) and various indicators of cognitive function. We analysed performance across multiple tests assessing domains of memory, processing speed/attention, language and executive function, and adjusted for demographic and socioeconomic characteristics. We found no significant association between PM2.5 and cognitive performance on any of the tests, after adjustment for covariates. Robustness checks on the main model found that the addition of a second pollutant – ozone – to the regression models changed the direction of association between PM2.5 and delayed recall score so that the association was now inverse. Investigations of possible effect modification by within-covariate groups yielded significant interactions with location, age group and area level deprivation for the verbal fluency task only. The results highlight the complexity of the underlying relationships, which differ by cognitive domain, population sub-group and pollutant.

Keywords: Air pollution, Particulate matter, cognition, ageing