Causes and Risk Factors
RA develops when part of the immune system, which is supposed to protect you from outside invaders, instead attacks your joints. It's not fully understood what causes the immune system to malfunction in this way, but RA is believed to be influenced by a combination of genetic susceptibility and environmental factors.
Your genes: People with a family history of RA are more likely to develop it themselves, and susceptibility to this disease has been traced to specific genes. But not everyone with a genetic predisposition gets RA, which suggests there may be other contributing factors.
Your environment: Environmental triggers may help set off RA in people who already have a genetic susceptibility. Research suggests a viral or bacterial infection is the most likely trigger, but other environmental factors that may play a part include prolonged exposure to cigarette smoke and/or silica dust.
Gender: Women are two to three times more likely than men to develop RA. The reason for this is unclear, although there's some evidence that hormones—particularly estrogens—may play a role in RA.
Age: RA usually begins between the ages of 30 and 60, but it can develop at any time.
Smoking: Smoking—and exposure to secondhand smoke—increases a person's risk of RA and may also increase the severity of the disease.
Ethnicity: RA occurs in people of all ethnicities, but some American Indian and Alaskan Native populations have a significantly higher incidence of RA than other ethnic groups.
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