614 - Farm History, Insecticide Use and Risk of Autoimmune Rheumatic Disease in the Women's Health Initiative Observational Study

Sunday, October 18, 2009: 5:15 PM
Auditorium (Pennsylvania Convention Center)
Christine G. Parks1, Brian T. Walitt2, Mary Pettinger3, Jiu-Chiuan Chen4, Anneclaire de Roos3, Julie Hunt3, Gloria Sarto5 and Barbara V. Howard6, 1National Institute of Environmental Health Science, Research Triangle Park, NC, 2Washington Hospital Center, Washington, DC, 3Fred Hutcinson Cancer Research Center, Seattle, WA, 4USC Keck School of Medicine, Los Angeles, 5University of Wisconsin Medical Center, Madison, 6Medstar Research Institute, Washington, DC
Presentation Number: 614

Purpose: Farming has been previously associated with the autoimmune rheumatic diseases (ARD), including rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE).  The exposure(s) underlying this association are not well-understood, and few studies have directly addressed the role of pesticides, including personal and residential insecticide use.  Method: Using data from the Women’s Health Initiative Observational Study (n=76,861, aged 50-79 years), we examined self-reported lifetime personal or commercial residential insecticide use and having lived or worked on a farm in relation to risk of incident ARD, confirmed by use of disease modifying anti-rheumatic drugs at year 3 of follow-up (n=213; 178 with RA only, 27 with SLE only, and 8 with both RA and SLE), and excluding unconfirmed cases.  Hazard ratios (HR) and 95% confidence intervals (CI) were estimated by multivariate models adjusting for age and covariates, including race, region, education, occupation, history of smoking, asthma, other autoimmune diseases, co-morbidity, and reproductive factors.   Results: Compared with never use, personal insecticide use (mixing or applying) was associated with ARD risk, with stronger associations among those with a greater frequency (age-adjusted HR=2.47; 95%CI 1.51, 4.03 for ≥ 6 times per year) and duration of use (age-adjusted HR=2.07; 95% CI 1.31, 3.25 for ≥ 20 years).  Increasing cumulative insecticide use (years X applications) also showed a significant trend of association (p=0.0004) with ARD risk, and these associations persisted after adjusting for farming and covariates.  Having lived or worked on a farm was also associated with ARD risk (age-adjusted HR=1.97; 95% CI 1.14, 3.42 for ≥20 years), but the effect size was diminished after adjusting for covariates and insecticide use.  Despite the small number of SLE cases, disease-stratified analyses indicated similar associations as seen for RA.  In those who had lived or worked on a farm, frequent commercial application to home or garden was also associated with ARD risk, even after adjusting for covariates and personal insecticide use (adjusted HR=2.73; 95%CI 1.1, 6.78 for ≥6 times per year).  Long-term commercial residential insecticide exposure was significantly associated with ARD risk regardless of farming history (age-adjusted HR=1.85; 95% CI 1.13, 3.04 for ≥20 years). Conclusion: Insecticide exposure may increase risk of ARD in post-menopausal women.  These findings, based on self-report, provide rationale for further investigation of specific personal and environmental insecticide exposures in relation to ARD.

Keywords: environmental factors, rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE)

Disclosure: C. G. Parks, None; B. T. Walitt, None; M. Pettinger, None; J. C. Chen, None; A. de Roos, None; J. Hunt, None; G. Sarto, None; B. V. Howard, None.