Autoimmune Diseases Take a Toll on Far More Women Than Men

What do rheumatoid arthritis, inflammatory bowel disease, and psoriasis have in common? They’re all autoimmune diseases—conditions in which a person’s immune system mistakenly attacks healthy tissue. Autoimmune diseases can produce symptoms that include everything from itchy, scaly skin and fatigue to joint pain and digestive problems.

“Autoimmune diseases are those in which cells and products of the immune system attack and damage one’s own tissues,” says Mary K. Crow, MD, chief of the division of rheumatology at Weill Cornell Medicine.

The immune system is a complex network of special cells and organs that protects the body from foreign invaders such as bacteria, viruses, and toxins. In autoimmune disease, instead of defending the body, the immune system makes autoantibodies that attack normal cells. At the same time, special cells called regulatory T cells fail to properly regulate the immune system.

More than 23 million Americans have an autoimmune disease; the most common ones in women are rheumatoid arthritis, psoriasis, thyroid diseases, systemic lupus erythematosus (lupus), and psoriatic arthritis.

More Awareness, More Diagnoses

In the past few decades, it seems like more health conditions have been identified as autoimmune, and more people have been diagnosed with one of these diseases.

“With research advances and increased awareness among physicians and the public, understanding of autoimmune diseases has grown. With that understanding and awareness, patients may be more likely to seek evaluation by physicians, and physicians are more knowledgeable regarding diagnosis of autoimmune diseases,” explains Dr. Crow.

It may seem like the numbers of patients are growing, but at least part of that may be attributed to more people discussing their symptoms with their doctors and being diagnosed.

Contributing Factors

“Genetic variability among all of us puts some of us at risk of developing an autoimmune disease. Some of those genetic variants are shared among different diseases, and others are more specific to a particular autoimmune disease. A recent, very large study calculated that 44 percent of the risk of developing lupus can be attributed to genetic factors,” says Dr. Crow.

Other contributors relate to environmental triggers, including many that are not yet identified. Environmental substances suspected of being triggers include toxic chemicals, heavy metals, and viral and bacterial infections.

“Chance also plays a role. Even identical twins exposed to the same environment do not always develop the same disease, and sometimes one twin develops disease and the other remains healthy,” explains Dr. Crow. “In summary, no clearly defined cause of autoimmune disease has been identified. There are likely to be many contributing factors, including genetics, environmental factors, and chance, that interact in a complex way.”

The Gender Gap

Among the estimated 23 million Americans who have an autoimmune disease, an estimated 18 million are women, and the remaining 5 million are men. For instance, rheumatoid arthritis (RA) affects an estimated 1.5 million adults in the U.S., with three times more women than men developing the disease. Why are women so much more susceptible than men to these diseases?

“This question has not yet been answered,” says Dr. Crow. “Our laboratory is studying males and females who get autoimmune disease to identify hints that might explain why females are so much more likely to get many autoimmune diseases, especially in the case of lupus, in which nine times more women than men get the disease.”

She continues, “Hormones likely contribute to some increased risk of women getting autoimmune disease, since estrogen can promote more activity in the immune system. The major, current theory relates to the X chromosome. Women have two X chromosomes, and almost all men only have one X chromosome. We know that the rare man who has two X chromosomes has an increased risk of developing autoimmune disease.”

Diagnosis and Treatment

The symptoms of early autoimmune disease include fatigue, low-grade fevers, muscle aches, swelling, and redness. Since there are many conditions that share these symptoms, it can take a while to identify the underlying cause as an autoimmune disease.

Tests that can aid in diagnosing autoimmune diseases include blood tests that look for antinuclear antibodies or measure the levels of various substances linked with autoimmune disease, such as immunoglobulins and C-reactive protein. Sometimes, multiple tests are required to reach a definitive diagnosis.

Treatment options vary depending on the type of disease that is diagnosed and the frequency and severity of symptoms. For example, Hashimoto’s thyroiditis (underproduction of thyroid hormones) can be treated with thyroid hormone replacement. Graves’ disease, which is an overproduction of thyroid hormones, is most often treated with radioactive iodine and/or anti-thyroid medications.

“Some of the most dramatic improvements in medical care have occurred through research and drug development focused on RA,” says Dr. Crow. “Methotrexate is often effective, but sometimes, it must be combined with so-called ‘biologic’ drugs, such as inhibitors of tumor necrosis factor, a molecule produced by the immune system that promotes inflammation in the joints.”

Biologics are a relatively new class of drugs (the first was approved by the FDA in 1998) that target specific parts of the immune system that promote inflammation. These drugs include infliximab (Remicade), adalimumab (Humira), etanercept (Enbrel), abatacept (Orencia), golimumab (Simponi), and several others. Many autoimmune diseases are treated with these drugs, and research is underway to determine which of these drugs is best suited for treatment of specific diseases.

Lifestyle choices such as diet and exercise appear to have some impact on autoimmune diseases.

“It is always wise to try to optimize lifestyle factors by eating a healthy diet, getting moderate exercise and sufficient sleep, and avoiding stress. However, even patients with autoimmune diseases who follow a healthy lifestyle often require medical therapy to gain control of their disease,” says Dr. Crow.

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