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Diabetes Status and Susceptibility to the Effects of PM2.5 Exposure on Cardiovascular Mortality in a National Canadian Cohort

Pinault, Laurena; Brauer, Michaelb; Crouse, Daniel L.c; Weichenthal, Scottd; Erickson, Andersb; van Donkelaar, Aarone; Martin, Randall V.e,f; Charbonneau, Shannong; Hystad, Perryh; Brook, Jeffrey R.i; Tjepkema, Michaela; Christidis, Tanyaa; Ménard, Richardj; Robichaud, Alainj; Burnett, Richard T.k

doi: 10.1097/EDE.0000000000000908
Environmental epidemiology
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Background: Diabetes is infrequently coded as the primary cause of death but may contribute to cardiovascular disease (CVD) mortality in response to fine particulate matter (PM2.5) exposure. We analyzed all contributing causes of death to examine susceptibility of diabetics to CVD mortality from long-term exposure.

Methods: We linked a subset of the 2001 Canadian Census Health and Environment Cohort (CanCHEC) with 10 years of follow-up to all causes of death listed on death certificates. We used survival models to examine the association between CVD deaths (n = 123,500) and exposure to PM2.5 among deaths that co-occurred with diabetes (n = 20,600) on the death certificate. More detailed information on behavioral covariates and diabetes status at baseline available in the Canadian Community Health Survey (CCHS)-mortality cohort (n = 12,400 CVD deaths, with 2,800 diabetes deaths) complemented the CanCHEC analysis.

Results: Among CanCHEC subjects, comention of diabetes on the death certificate increased the magnitude of association between CVD mortality and PM2.5 (HR = 1.51 [1.39–1.65] per 10 μg/m3) versus all CVD deaths (HR = 1.25 [1.21–1.29]) or CVD deaths without diabetes (HR = 1.20 [1.16–1.25]). Among CCHS subjects, diabetics who used insulin or medication (included as proxies for severity) had higher HR estimates for CVD deaths from PM2.5 (HR = 1.51 [1.08–2.12]) relative to the CVD death estimate for all respondents (HR = 1.31 [1.16–1.47]).

Conclusions: Mention of diabetes on the death certificate resulted in higher magnitude associations between PM2.5 and CVD mortality, specifically among those who manage their diabetes with insulin or medication. Analyses restricted to the primary cause of death likely underestimate the role of diabetes in air pollution–related mortality. See video abstract at, http://links.lww.com/EDE/B408.

From the aHealth Analysis Division, Statistics Canada, Ottawa, Ontario, Canada

bUniversity of British Columbia, Vancouver, British Columbia, Canada

cUniversity of New Brunswick, Fredericton, New Brunswick, Canada

dMcGill University, Montreal, Quebec, Canada

eDalhousie University, Halifax, Nova Scotia, Canada

fHarvard-Smithsonian Center for Astrophysics, Cambridge, MA

gCollege of Family Physicians of Canada, Kingston, Ontario, Canada

hOregon State University, Corvallis, OR

iUniversity of Toronto, Toronto, Ontario, Canada

jAir Quality Research Division, Environment and Climate Change Canada, Dorval, Quebec, Canada

kPopulation Studies Division, Health Canada, Ottawa, Ontario, Canada.

Submitted December 7, 2017; accepted July 27, 2018.

Data Access: Both of the analytical cohorts used (2001 CanCHEC and 2001 CCHS-mortality cohort) are available to researchers to access through Statistics Canada’s Research Data Centre program. The programs used to assign environmental exposures (PCCF+ and postal code imputation) are also available to researchers through subscription/request. Environmental exposures are available upon request to the original authors of the data. The analytical code used was all standard SAS code (e.g., data steps, proc phreg).

Research described in this article was conducted under contract to the Health Effects Institute (HEI), an organization jointly funded by the United States Environmental Protection Agency (EPA; assistance award number: R-82811201) and certain motor vehicle and engine manufacturers. The contents of this article do not necessarily reflect the views of HEI, or its sponsors, nor do they necessarily reflect the views and policies of the EPA or motor vehicle and engine manufacturers.

The authors report no conflicts of interest.

Supplemental digital content is available through direct URL citations in the HTML and PDF versions of this article (www.epidem.com).

Correspondence: Daniel L. Crouse, Department of Sociology, University of New Brunswick, 9 Macaulay Lane, Tilley Hall, Room 20, Fredericton, New Brunswick, Canada, E3B 5A3. E-mail: dlcrouse@gmail.com.

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