Sunlight Exposure, Sun-Protective Behavior, and Anti–Citrullinated Protein Antibody Positivity: A General Population-Based Study in Quebec, Canada
Supported by the Canadian Institutes of Health Research (PJT-159682). ACPA assay kits were a gift from Inova Diagnostics, San Diego, California.
No potential conflicts of interest relevant to this article were reported.
Abstract
Objective
To examine associations between sunlight exposure and anti–citrullinated protein antibodies (ACPAs) using general population data in Quebec, Canada.
Methods
A random sample of 7,600 individuals (including 786 subjects who were ACPA positive and 201 self-reported rheumatoid arthritis [RA] cases) from the CARTaGENE cohort was studied cross-sectionally. All subjects were nested in 4 census metropolitan areas, and mixed-effects logistic regression models were used to calculate odds ratios (ORs) and 95% confidence intervals (95% CIs) for ACPA positivity related to sunlight exposure, adjusting for sun-block use, industrial fine particulate matter (PM2.5) exposures, smoking, age, sex, French Canadian ancestry, and family income. We also performed sensitivity analyses excluding subjects with RA, defining ACPA positivity by higher titers, and stratifying by age and sex.
Results
The adjusted ORs and 95% CIs did not suggest conclusive associations between ACPA and sunlight exposure or sun-block use, but robust positive relationships were observed between industrial PM2.5 emissions and ACPA (OR 1.19 per μg/m3 [95% CI 1.03–1.36] in primary analyses).
Conclusion
We did not see clear links between ACPA and sunlight exposure or sun-block use, but we did note positive associations with industrial PM2.5. Future studies of sunlight and RA (or ACPA) should take air pollution exposures into account.