Long-term Exposure to Ambient Air Pollution and Trajectories of Cognitive Decline in Northern Manhattan

Age-related cognitive decline is a growing public health issue as increases in life expectancy are expected to substantially raise the prevalence of cognitive impairment and dementia. An estimated 46.8 million individuals are currently living with dementia, with the global prevalence expected to double every 20 years. Emerging evidence suggests that ambient air pollution from traffic and other sources may be an important risk factor for cognitive decline in addition to its association with other cardiovascular and neurological outcomes. The aim of this dissertation was to first investigate the association between long-term exposure to ambient air pollution and cognitive decline among older adults in an urban population within Northern Manhattan. I then set out to assess specific mechanisms involved in the association between long-term exposure to ambient air pollution and cognitive decline, specifically investigating the ApoE4 allele, age, and current smoking behavior as effect modifiers of the association between long-term exposure to ambient air pollution and cognitive decline. I found evidence of an adverse effect of ambient air pollution on the cognitive functioning of older adults. Overall, exposure to higher levels of ambient air pollution was highly predictive of lower cognitive scores, but at baseline only. Contrary to the current hypothesis, limited evidence was found for an association between estimates of air pollution and trajectories of cognitive decline. The patterns of effect were similar across pollutant types and cognitive domains in this aging, urban population. I found strong evidence of effect modification by smoking status, where contrary to the hypothesis; the overall effects of ambient air pollution on cognition and cognitive decline were stronger among individuals who never smoked. The impact of effect modification by age category was most prominent in the memory and language cognitive domains. Among individuals less than 75 years old at baseline, there was a stronger association between a one IQR increase in air pollutants and cognitive domain scores at baseline as compared to individuals 75 years and older. I did not observe conclusive evidence of an association between air pollution and cognition in models stratified by APOE-4 status. To my knowledge, this is the largest study to analyze the association of ambient air pollution on cognition and cognitive decline over time in a racially and ethnically diverse sample. These results further support the current evidence on the role of air pollution on accelerated cognitive aging and brain health.