Women living in the northeastern U.S. may be more susceptible to the autoimmune disease rheumatoid arthritis (RA) due to a lack of exposure to the sun, which can cause a vitamin D deficiency.

Researchers looked at data from a long-term study of U.S. female nurses between 1988 and 2002. They looked at where the participants lived, their health outcomes and behavioral risk factors. Their findings were based on 461 women who had RA, compared to a large control group of 9,220.

The study found that women in states like Vermont, New Hampshire and southern Maine were more likely to report being diagnosed with RA.

"There’s higher risk in the northern latitudes," said the study’s lead author, Dr. Veronica Vieira. "This might be related to the fact that there’s less sunlight in these areas, which results in a vitamin D deficiency."

RA is a chronic inflammatory disease that is characterized by swelling and redness, and can wear down the cartilage between bones.

Vitamin D is found in foods like milk, fish and eggs as well as cod liver oil and nutritional supplements. It is also produced in the body after exposure to the sun. It is believed that as little as 10 minutes of daily sun exposure is enough to prevent deficiencies.