Insecticide use and risk of rheumatoid arthritis and systemic lupus erythematosus in the Women’s Health Initiative Observational Study – Source: Arthritis Care & Research, Feb 2011

Objective: Farming and agricultural pesticide use has been associated with 2 autoimmune rheumatic diseases – rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE).

However, risk associated with other residential or work place insecticide use is unknown.

Methods: We analyzed data from the Women's Health Initiative Observational Study (n = 76,861 postmenopausal women, ages 50–79 years). Incident cases (n = 213: 178 for RA, 27 for SLE, and 8 for both) were identified based on self-report and use of disease-modifying antirheumatic drugs at year 3 of followup.

We examined self-reported residential or work place insecticide use (personally mixing/applying by self and application by others) in relation to RA/SLE risk, overall and in relation to farm history. Hazard ratios (HRs) and 95% confidence intervals (95% CIs) were adjusted for age, race, region, education, occupation, smoking, reproductive factors, asthma, other autoimmune diseases, and comorbidities.

Results: Compared with never used, personal use of insecticides was associated with increased RA/SLE risk, with significant trends for:

• Greater frequency (HR 2.04, 95% CI 1.17–3.56 for 6 or more times/year) [Note: a hazard ratio of 1.0 would indicate no difference in rigk. The HR of 2.04 indicates the average risk of RA/SLE was more than double during the 3-year tracking period among those who personally used an insecticide regularly.]

• And duration (HR 1.97, 95% CI 1.20–3.23 for 20 or more years).

Risk was also associated with long-term insecticide application by others (HR 1.85, 95% CI 1.07–3.20 for 20 or more years) and frequent application by others among women with a farm history (HR 2.73, 95% CI 1.10–6.78 for 6 or more times/year).

Conclusion: These results suggest residential and work place insecticide exposure is associated with the risk of autoimmune rheumatic diseases in postmenopausal women. Although these findings require replication in other populations, they support a role for environmental pesticide exposure in the development of autoimmune rheumatic diseases.

Source: Arthritis Care & Research, Feb 2011;63(2)184-194. Parks CG, Walitt BT, Pettinger M, Chen J, de roos AJ, Hunt J, Sarto G, Howard BV. National Institute for Environmental Health Science, Durham, North Carolina; Washington Hospital Center, Washington, DC; Fred Hutchinson Cancer Research Center, Seattle, Washington; University of California Keck School of Medicine, Los Angeles; University of Wisconsin Medical Center, Madison; MedStar Health Research Institute, Washington, DC. [Email:]

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