Background/Purpose: To estimate the degree to which fine particulate (PM2.5) air pollution is associated with systemic autoimmune rheumatic diseases (SARDs).

Methods: We used population-based administrative data from Alberta (1993-2007) and Quebec (1989-2010). The SARD case definition was based on at least 2 physician billing claim codes, or at least 1 rheumatology billing code, or at least 1 hospitalization diagnostic code (for systemic lupus, Sjogren’s Syndrome, scleroderma, polymyositis, dermatomyositis, or undifferentiated connective tissue disease). Bayesian hierarchical latent class regression models estimated the probability that any given resident was a SARD case, given our three case definitions. Mean 2001-2006 residential exposures to ambient PM2.5 levels were assigned using satellite-derived data for Dissemination Area regions in Alberta, and Local Community ServicesCentre (CLSC) regions in Quebec (both assigned from postal code of residence). The sum of individual level probabilities provided the total cases per region in each province, according to age, sex, urban-versus-rural residence, income, and PM2.5 levels. In Alberta, we also stratified by First-Nations(FN) status, which in Alberta represents about 3% of the population (Blackfoot, Cree, Chipewyan, Dene, Sarcee, Stoney /Nakoda Sioux, and others). The hierarchical model generated odds ratio (OR) estimates for being a SARD case, based on age, sex, urban-versus-rural residence, income, and PM2.5 levels. The model accounted concurrently for these characteristics, as well as an interaction term between age and sex. The model generated Bayesian 95% credible intervals (CrI, which are similar to the non-Bayesian confidence interval) for the OR estimates.

Results: The probability of being a SARD case was higher among females versus males and for residents aged > 45 versus younger, with the highest ORs for older females. Independently, the odds of being a SARDs case increased with PM2.5 levels. In Alberta, the effect was slightly greater for FN residents. Specifically, in Alberta, when we used a continuous variable for PM2.5, the adjusted OR (interpreted as increase in SARDs per unit increase in PM25) in FN residents was 1.38 (95% CrI 1.14, 1.68) whereas in non-FN Alberta residents the adjusted OR was 1.05 (95% CrI 1.01, 1.08). In Quebec, where information on FN status (1% of the Quebec population) was not available, the adjusted OR for PM2.5 as a continuous variable, was 1.05 (95% CI 1.05, 1.06).

Conclusion: Adjusting for demographics, exposure to PM2.5 is associated with an increased risk of SARDs. Our data suggest that FN populations may be particularly vulnerable to this effect. Improving air quality across the continent appears to be an important way to reduce chronic disease burden, not only for respiratory and cardiac disease, but also systemic autoimmune rheumatic diseases.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/fine-particulate-air-pollution-and-systemic-autoimmune-rheumatic-disease-in-two-canadian-provinces/