Nested case-control study of autoimmune disease in an asbestos-exposed population

Objective: To explore the potential association between asbestos exposure and risk of autoimmune disease, we conducted a case-control study among a cohort of 7,307 current and former residents of Libby, Montana, a community wth historical occupational and environmental exposure to asbestos-contaminated vermiculite. Methods: Cases were defined as those who reported having one of three systemic autoimmune diseases (SAIDs): systemic lupus erythematosus, scleroderma or rheumatoid arthritis (RA). Controls were randomly selected at a 3:1 ratio from among the remaining 6,813 screening participants using frequency-matched age and sex groupings. Results: The odds ratios (ORs) and 95% confidence intervals (Cls) for SAIDs among those ≥ 65 years of age who had worked fo the vermiculite mining company were 2.14 (95% CI, 0.90-5.10) for all SAIDs and 3.23 (95% CI, 1.31-7,96) tar RA. In this age group, exposure to asbestos while in the military was also an independent risk fitctor, resulting in a tripling in risk. Other measures of occupational exposure to vermiculite indicated 54% and 65% increased risk for SAIDs and RA respectively. Those who had reported frequent contact with vermiculite through vaious exposure pathwas also demonstrated elevated risk for SAIDs and RA. We found increasing risk estimated for SAIDs with increasing numbers of reported vermiculite exposure pathways (p < 0.001). Conclusion: These preliminary findings support the hypothesis that asbestos exposure is associated with autoimmune disease. Refined measurements of asbestos exposure and SAID status among this cohort will help to further clarify the relationship between these variales.