Insecticides May Raise Risk of Lupus, RA

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Oct. 20, 2009 (Philadelphia) — Women who spray their homes and gardens withinsecticides may be placing themselves at risk for rheumatoid arthritis andlupus, a study shows. 

In a study of more than 75,000 women, those who used insecticides sixor more times a year had nearly two-and-a-half times the risk of developing theautoimmune diseases than women who adopted a live-and-let-live attitude towardbugs. 

Similarly, the risk more than doubled if bug sprays were used in the homefor 20 or more years.

Hiring a gardener or commercial company to apply insecticides also resultedin a doubling of risk, but only if they were used long-term, says Christine G.Parks, PhD, an epidemiologist with the National Institute of EnvironmentalHealth Sciences in Research Triangle Park, N.C.

“Our new results provide support for the idea that environmental factors mayincrease susceptibility or trigger the development of autoimmune diseases insome individuals,” she says.

Although the study doesn’t prove cause and effect, “we need to startthinking about what chemicals or other factors related to insecticide use couldexplain these findings,” Parks tells WebMD.

The researchers used data from the Women’s Health Initiative ObservationalStudy of 76,861 postmenopausal, predominantly white women ages 50 to 79. Of thetotal, 178 of them had rheumatoid arthritis and 27 had lupus. An additionaleight women had both disorders. As part of the study, the women were asked anumber of questions relating to farming and insecticide use.

“Importantly, the relationships we observed were not explained by otherfactors that we considered, including farm history, age, race, ethnicity,socioeconomic factors such as education and occupation, smoking and other riskfactors for disease,” Parks says.

Interestingly, a history of working or living on a farm did not appear toincrease risk of rheumatoid arthritis or lupus in the study, she adds. Previousstudies have linked farming and agricultural pesticide exposure to thedisorders.

The findings were presented at the annual meeting of the American College ofRheumatology.

Studies show that as many as three-fourths of U.S. households have reportedusing insecticides in the home or garden, and 20% of households have appliedinsecticides in the last month, according to Parks.

“Insecticide exposure in the home can be quite persistent because they don’tbreak down in the home environment,” Parks says.

“The findings are fairly compelling” because they show the greater andlonger the exposure, the greater the risk, says Darcy Majka, MD, assistantprofessor of medicine at Northwestern University Feinberg School ofMedicine.

“Now we have to go back to the bench. Which products pose a risk? Is skinexposure [to blame], or inhaling?” she says.

For now, Majka tells WebMD, “The important thing is to follow the directions[on the product] and take other measures to limit chemical exposure.”

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