Long-term exposure to ambient air pollution and incident dementia among older adults in Northern Manhattan

Abstract

BACKGROUND AND AIM: Age-related cognitive decline is a growing public health issue as increases in life expectancy and the aging of the population are expected to raise the prevalence of cognitive impairment and dementia. An estimated 47 million individuals live with dementia, with the global prevalence expected to double every 20 years. Evidence is growing that suggests that ambient air pollution from traffic and other sources may be an important risk factor for cognitive decline and dementia. We evaluated the association between long-term exposure to ambient air pollution and incident dementia in a cohort of urban dwelling older adults. METHODS: The Washington Heights Inwood Community Aging Project (WHICAP) is a prospective, community-based study of aging and dementia in older adults 65 years old in Northern Manhattan, NYC. At enrollment, participants underwent neuropsychological testing and medical examinations. Follow-up assessments occurred every 18-24 months. Cases are adjudicated for dementia at each follow-up by trained neuropsychologists. We used Cox proportional hazard models with age as the time scale to evaluate the association between markers of ambient air pollution (nitrogen dioxide [NO2]) and fine particulate matter [PM2.5]) at enrollment and incident dementia, adjusting for sociodemographic factors and temporal trends. RESULTS:Among 4,122 dementia-free participants with an average of 8 years of follow-up, 14% (n=591) were diagnosed with incident dementia. Participants living in the highest level of ambient PM2.5 exposure were 17% more likely than those in the lowest exposure quartile to develop incident dementia in fully adjusted models (HRadj 1.17 95% CI 0.76, 1.80). Results for NO2 were similar (HRadj = 1.14 95% CI 0.68, 1.89, for highest versus lowest quartile). CONCLUSIONS:These results add to the growing evidence base implicating the role of air pollution on accelerated cognitive aging and brain health, particularly in aging urban populations. KEYWORDS: Air pollution, epidemiology, Neurodegenerative outcomes