Abstract
BackgroundEmerging evidence links road proximity and air pollution with cognitive impairment. Joint effects of noise and greenness have not been evaluated. We investigated associations between road proximity and exposures to air pollution, and joint effects of noise and greenness, on non-Alzheimer’s dementia, Parkinson’s and Alzheimer’s disease and multiple sclerosis within a population-based cohort.MethodsWe assembled administrative health database cohorts of 45–84 year old residents (N ~ 678,000) of Metro Vancouver, Canada. Cox proportional hazards models were built to assess associations between exposures and non-Alzheimer’s dementia and Parkinson’s disease. Given reduced case numbers, associations with Alzheimer’s disease and multiple sclerosis were evaluated in nested case-control analyses by conditional logistic regression.ResultsRoad proximity was associated with all outcomes (e.g. non-Alzheimer’s dementia hazard ratio: 1.14, [95% confidence interval: 1.07–1.20], for living < 50 m from a major road or < 150 m from a highway). Air pollutants were associated with incidence of Parkinson’s disease and non-Alzheimer’s dementia (e.g. Parkinson’s disease hazard ratios of 1.09 [1.02–1.16], 1.03 [0.97–1.08], 1.12 [1.05–1.20] per interquartile increase in fine particulate matter, Black Carbon, and nitrogen dioxide) but not Alzheimer’s disease or multiple sclerosis. Noise was not associated with any outcomes while associations with greenness suggested protective effects for Parkinson’s disease and non-Alzheimer’s dementia.ConclusionsRoad proximity was associated with incidence of non-Alzheimer’s dementia, Parkinson’s disease, Alzheimer’s disease and multiple sclerosis. This association may be partially mediated by air pollution, whereas noise exposure did not affect associations. There was some evidence of protective effects of greenness.
Highlights
Emerging evidence links road proximity and air pollution with cognitive impairment
In the cohort of non-Alzheimer’s dementia (NAD), road proximity was moderately correlated with air pollution (e.g. r = 0.49 between major road < 50 m or highway < 150 m and black carbon)
A study in Hong Kong reported that including vertical gradient information did not lead to meaningful differences or changes in estimates of effect for the association between air pollution with mortality [90]. In this large population-based study, living near roads was linked with higher incidence of NAD, Parkinson’s disease (PD), Alzheimer’s disease (AD) and multiple sclerosis (MS)
Summary
Emerging evidence links road proximity and air pollution with cognitive impairment. Joint effects of noise and greenness have not been evaluated. We investigated associations between road proximity and exposures to air pollution, and joint effects of noise and greenness, on non-Alzheimer’s dementia, Parkinson’s and Alzheimer’s disease and multiple sclerosis within a population-based cohort. Neurological disorders, such as Parkinson’s disease, are one of the leading causes of disability in Canada and in other high income countries [1]. They are associated with a range of adverse impacts that pose daily challenges to patients, their families and health care systems [1, 2]. Alzheimer’s disease is the most commonly diagnosed type of dementia [11] with previous studies classifying dementia into non-Alzheimer’s dementia and Alzheimer’s disease [12,13,14]
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