Living at higher latitudes may boost women's risk of rheumatoid arthritis (RA), according to a geographical analysis of a major prospective study.
The analysis by area of residence among participants in the Nurses' Health Study who developed RA, found that those women who had lived at higher latitudes were at generally greater risk than their more southern counterparts (P=0.034), said Verónica M. Vieira, DSc, of Boston University School of Public Health, and colleagues.
In particular, the upper northeastern region of the U.S. appeared to be a hotbed of RA risk compared with other areas, they reported in the July issue of Environmental Health Perspectives.
These results add to the mysterious link between autoimmune disorders and living in areas at higher latitudes, including higher RA rates seen in northern versus southern Europe and a younger age of onset in Canada versus Mexico, Vieira's group noted.
So, the researchers did a spatial analysis between geographic location of residence and RA risk at the individual patient level in the Nurses' Health Study.
The original cohort of 121,700 female nurses had been ages 30 to 55 at baseline in 1976 and were initially spread across 11 states (California, Connecticut, Florida, Massachusetts, Maryland, Michigan, New Jersey, New York, Ohio, Pennsylvania, and Texas). By 2002, the cohort had spread across 50 states.
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