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Study Shows Increased Risk of Autoimmune Diseases in Women Who Use Insecticides

By Charlene Laino
WebMD Health News

Reviewed by Louise Chang, MD

Oct. 20, 2009 (Philadelphia) -- Women who spray their homes and gardens with insecticides may be placing themselves at risk for rheumatoid arthritis and lupus, a study shows.

In a study of more than 75,000 women, those who used insecticides six or more times a year had nearly two-and-a-half times the risk of developing the autoimmune diseases than women who adopted a live-and-let-live attitude toward bugs.

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

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

"Our new results provide support for the idea that environmental factors may increase susceptibility or trigger the development of autoimmune diseases in some individuals," she says.

Although the study doesn't prove cause and effect, "we need to start thinking about what chemicals or other factors related to insecticide use could explain these findings," Parks tells WebMD.

The researchers used data from the Women's Health Initiative Observational Study of 76,861 postmenopausal, predominantly white women ages 50 to 79. Of the total, 178 of them had rheumatoid arthritis and 27 had lupus. An additional eight women had both disorders. As part of the study, the women were asked a number of questions relating to farming and insecticide use.

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

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

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

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

"Insecticide exposure in the home can be quite persistent because they don't break down in the home environment," Parks says.

"The findings are fairly compelling" because they show the greater and longer the exposure, the greater the risk, says Darcy Majka, MD, assistant professor of medicine at Northwestern University Feinberg School of Medicine.

"Now we have to go back to the bench. Which products pose a risk? Is skin exposure [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."

Symptoms

If you have lupus (systemic lupus erythematosus, or SLE), you may be extremely tired, have skin rashes, or have joint pain. If the disease is more serious, you may have problems with your kidneys, heart, lungs, blood, or nervous system.

Lupus symptoms depend on what body organs are affected and how seriously they are affected.

· Fatigue : Nearly all people with lupus have mild to extreme fatigue. Even mild cases of lupus cause an inability to engage in daily activities and exercise. Increased fatigue is a classic sign that a symptom flare is about to occur.

· Joint and muscle pain : Most people with lupus have joint pain (arthritis) at some time. About 70% of people with lupus report that joint and muscle pain was their first sign of the disease. Joints may be red and warm, and may swell. Morning stiffness may also be felt. Lupus arthritis often occurs on both sides of the body at the same time, particularly in the wrists, small joints of the hands, elbows, knees, and ankles.

· Skin problems : Most people with lupus develop skin rashes. These rashes are often an important clue to the diagnosis. In addition to the butterfly rash over the cheeks and bridge of the nose, other common skin symptoms include skin sores or flaky red spots on the arms, hands, face, neck, or back; mouth or lip sores; and a scaly, red or purple raised rash on the face, neck, scalp, ears, arms, and chest.

· Sensitivity to light : Exposure to ultraviolet light (such as sunlight or tanning parlors) typically worsens the skin rash and can trigger lupus flares. Sensitivity to light affects many of those with lupus, with fair-skinned people with lupus tending to be more sensitive.

· Nervous system symptoms : The majority of people with lupus develop nervous system problems, most commonly headaches, depression, or anxiety. Memory loss is less common.

· Heart problems : People with lupus may develop inflammation of the heart sac (pericarditis), which may cause severe, sudden pain in the center of the left side of the chest that may spread to the neck, back, shoulders, or arms.

· Mental health problems : People with lupus may develop problems such as anxiety and depression. Such problems can be caused by lupus, the medications used to treat it, or the stress of coping with chronic illness.

· Fever : Most people with lupus will sometimes have a low-grade fever related to the disease. Fever is sometimes a first sign of the disease.

· Changes in weight : Many people with lupus lose weight when their disease is active (flaring).

· Hair loss : People with lupus may experience periods of hair loss, either in patches or spread evenly over the head. This hair loss is usually not permanent.

· Swollen glands : Many people with lupus eventually develop swollen lymph glands during a flare.

· Raynaud's phenomenon: Some people with lupus have this condition. It affects the small vessels that supply blood to the skin and the soft tissues under the skin of the fingers and toes, causing them to turn white and/or blue or red. The skin affected will feel numb, tingly, and cold to the touch.

· Inflammation of blood vessels in the skin (cutaneous vasculitis): Inflammation or bleeding from the blood vessels can lead to small or large blue spots or small reddish spots on the skin or nail beds.

· Swelling of the hands and feet : Some people with lupus have kidney problems, which can prevent extra fluids from being removed from the body tissues. As fluid collects, the hands and feet may swell.

· Anemia : Anemia is a decrease in the amount of the oxygen-carrying substance (hemoglobin) found in red blood cells. Many people with an ongoing disease such as lupus develop anemia because they don't have enough red blood cells.

There are other conditions with symptoms similar to lupus.

WebMD Medical Reference from Healthwise