| Nested Case–Control Study of Autoimmune Disease in an Asbestos-Exposed Population Curtis W. Noonan,1 Jean C. Pfau,1 Theodore C. Larson,2 and Michael R. Spence3 1Center for Environmental Health Sciences, University of Montana, Missoula, Montana, USA; 2Agency for Toxic Substances and Disease Registry, Centers for Disease Control and Prevention, Atlanta, Georgia, USA; 3Montana Department of Health and Human Services, Helena, Montana, USA Abstract
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 with 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 (CIs) for SAIDs among those ≥ 65 years of age who had worked for 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) for RA. In this age group, exposure to asbestos while in the military was also an independent risk factor, 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 various exposure pathways also demonstrated elevated risk for SAIDs and RA. We found increasing risk estimates 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 variables. Key words: asbestos, autoimmune, Libby, lupus, rheumatoid arthritis, scleroderma, vermiculite. Environ Health Perspect 114:1243–1247 (2006) . doi:10.1289/ehp.9203 available via http://dx.doi.org/ [Online 30 May 2006]
Address correspondence to C.W. Noonan, Center for Environmental Health Sciences, Skaggs 154, University of Montana, Missoula, MT 59812 USA. Telephone: (406) 243-4957. Fax: (406) 243-2807. E-mail: curtis.noonan@umontana.edu We thank all the participants of the Agency for Toxic Substances and Disease Registry–funded screening program. Special thanks to C. Holoboff and staff of the Montana Asbestos Surveillance and Screening Activity for assisting with the follow-up mailing. Funding was provided under grants from the Centers for Disease Control and Prevention (R01 CCR822092-02) and the National Center for Research Resources (COBRE P20RR017670) . The authors declare they have no competing financial interests. Received 27 March 2006 ; accepted 30 May 2006.
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