Newswise — Insecticide exposure may increase the risk of developing two well known autoimmune rheumatic diseases in post-menopausal women, according to research presented this week at the American College of Rheumatology Annual Scientific Meeting in Philadelphia, Pa.
Rheumatic disease is a term used to describe hundreds of diseases and conditions that affect the joints, muscles, and tendons, including two of the most common systemic autoimmune diseases, rheumatoid arthritis and lupus.
Farming and agricultural pesticide exposure has been linked to the development of rheumatoid arthritis and lupus, but it is unclear whether pesticide exposure in other settings might also increase risk of disease.
Researchers recently studied the relationship between personal insecticide use and commercial residential insecticide exposures and the development of these diseases in a group of women from across the United States.
Using data from the Women’s Health Initiative Observational Study, which included information from generally healthy postmenopausal women, researchers identified 76,861 women who were ages 50 to 79 years old and examined their lifetime personal or commercial residential insecticide use (as reported by the participants) and noted whether or not they had lived or worked on a farm.
Researchers then determined which women at a later visit reported that they had been newly diagnosed with either rheumatoid arthritis or lupus and who also reported using disease modifying anti-rheumatic drugs, which typically treat RA and other connective tissue diseases. They then compared information on insecticide use and other factors that might also be risk factors RA or lupus, to determine if there is a connection between any of these factors and development of disease.
Of the 76,861 people studied, 178 had newly developed RA, 27 newly developed lupus, and eight had both. Risk of developing RA or lupus was higher for women who reported more insecticide use, regardless of whether they ever lived or worked on a farm. These results were not changed after adjusting their results to consider age, race, farming history, geographical region, education, occupation, history of smoking, asthma, as well as other diseases and conditions (including other autoimmune diseases) and reproductive factors. Researchers found that—when compared to people who had never used insecticides—those who had personally mixed or applied insecticides were at greater risk of developing a rheumatic disease – with more than double the risk in those women reporting more frequent or longer duration of use.
The researchers believe these findings suggest that exposure to insecticides may increase the risk of developing RA or lupus in the general population, not only in the farming environment.
“Although suggestive, we need to start thinking about what chemicals or other factors related to insecticide use could explain these findings,” says Christine G. Parks, PhD; epidemiologist, National Institute of Environmental Health Sciences, National Institutes of Health, Bethesda, Md., and the lead investigator in the study. “Our results also provide support for the idea that environmental factors may increase susceptibility or trigger the development of autoimmune diseases in some individuals.”
The ACR is an organization of and for physicians, health professionals, and scientists that advances rheumatology through programs of education, research, advocacy and practice support that foster excellence in the care of people with or at risk for arthritis and rheumatic and musculoskeletal diseases. For more information on the ACR’s annual meeting, see www.rheumatology.org/annual.
Editor’s Notes: Dr. Parks will present this research during the ACR Annual Scientific Meeting at the Pennsylvania Convention Center at 5:15 PM on Sunday, October 18 in the Auditorium. Dr. Parks will be available for media questions and briefing at 8:30 AM on Monday, October 19 in the on-site press conference room, 109 A.
Presentation Number: 614
Farm History, Insecticide Use and Risk of Autoimmune Rheumatic Disease in the Women's Health Initiative Observational Study
Christine G. Parks, PhD, Epidemiology Branch, National Institute of Environmental Health Science, Research Triangle Park, NC Brian T. Walitt, MD, Rheumatology, Washington Hospital Center, Washington, DC Mary Pettinger, MS, Fred Hutcinson Cancer Research Center, Seattle, WA Jiu-Chiuan Chen, MD, PhD, USC Keck School of Medicine, Los Angeles, CA Anneclaire de Roos, PhD, Fred Hutcinson Cancer Research Center, Seattle, WA Julie Hunt, PhD, Fred Hutcinson Cancer Research Center, Seattle, WA Gloria Sarto, M.D., PhD, University of Wisconsin Medical Center, Madison, WI Barbara V. Howard, PhD, Medstar Research Institute, Washington, DC
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.
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.
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