BOSTON—Women living in northern latitudes might be at a higher risk of rheumatoid arthritis (RA), according to new research from the Boston University School of Public Health. Led by Verónica Vieira, MS, DSc, associate professor of environmental health, the research reviewed data from the Nurses' Health Study, a long-term cohort study of U.S. female nurses, and published the results online ahead of print in the journal Environmental Health Perspectives.
The spatial analysis included data on 461 women with RA and 9,022 women without RA (control group), reviewing their residential addresses, health outcomes and behavioral risk factors between 1988 and 2002.
The results showed a statistically significant geographical area of higher RA risk, which included more northern states such as Vermont, New Hampshire and Southern Maine. Acknowledging the role vitamin D deficiency is hypothesized to play in autoimmune diseases, the researchers suggested lack of sunlight in the northern latitudes could be a factor in the risk trend found with RA.
They wrote, "A geographic association with northern latitudes has also been observed for multiple sclerosis and Crohn's disease, other autoimmune diseases that may be mediated by reduced vitamin D from decreased solar exposure and the immune effects of vitamin D deficiency.”
“The results were unexpected," Vieira said. "Prior to the analysis, we were more interested in the relationship with air pollution. I hadn't given latitudes much thought."
In addition, the results indicated possible connection between increased RA risk and timing of residency in sun-starved locations. "Slightly higher odds ratios were observed for the 1988 analysis suggesting that long term exposure may be more important than recent exposure," the report noted.
