Outdoor Air Pollution in Canada: Associations with Major Depressive Episodes and Depressive Symptoms
Date
2021-07-08
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Objective: The objective of this thesis was to assess whether exposure to increased levels of outdoor air pollution is associated with an increased prevalence of major depression. Methods: The prevalence of major depressive episode (MDE) from 2011 to 2014 and moderate-severe depressive symptoms of major depression from 2015-2016 were derived from six consecutive survey years of the annual Canadian Community Health Survey (CCHS). The Canadian Urban Environmental Research Consortium provided estimates of the annual average concentration of fine particulate matter ≤2.5 micrometers (µm) in diameter (PM2.5) (2012-2015), ozone (O3) (2013-2015), sulfur dioxide (SO2) (2011-2015), and nitrogen dioxide (NO2) (2012). Outdoor air pollution data was linked with the annual CCHS survey data via 6-digit residential postal codes. Long-term exposure to increased levels of residential outdoor air pollution was defined by the upper quartile of the annual average concentration of PM2.5, O3, SO2, and NO2. Log-binomial models were used to estimate prevalence ratios with corresponding 95% confidence intervals. Single outdoor air pollutant models included adjustment for age, sex, marital status, income, education, employment status, urban versus rural households, cigarette smoking, and chronic illness. Results: Overall, these findings did not suggest that exposure to increased levels of outdoor air pollution is associated with an elevated prevalence of MDE or moderate-severe symptoms of major depression. No evidence of modification or confounding was observed. Conclusions: The analysis did not find evidence that outdoor air pollution is associated with major depression in Canada. Although outdoor air pollution was not identified as a neighbourhood-level determinant of major depression, these results should be generalized to other countries with caution. The null results that we observed may be due to the relatively low levels of outdoor air pollution in Canada. Air pollution at these levels may not be sufficient to activate the relevant mechanisms of major depression (e.g., inflammation, aggravation of chronic conditions, production of depressive symptoms). Future research should examine whether outdoor air pollution is linked to major depression in regions with higher levels of outdoor air pollution or during intervals of elevated exposure such as those that may occur during natural disasters.
Description
Keywords
Citation
Dores, A. K. (2021). Outdoor Air Pollution in Canada: Associations with Major Depressive Episodes and Depressive Symptoms (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.