It's been known for years that autoimmune diseases affect more women than men. There are theories why - some of which are explored in a Stanford Medicine magazine article I helped research last year - but, for the most part, researchers are still in the dark. And now immunologists have yet another mystery to explore: why rates of one such disease, rheumatoid arthritis, are increasing in women after decades of decline.
MedPage Today reports:
Between 1995 and 2007, the incidence of RA increased by a modest but significant 2.5% per year... among women residing in Olmsted County, Minn., according to Elena Myasoedova, MD, PhD, and colleagues from the Mayo Clinic, in Rochester, Minn.
A similar increase was not observed among men, who had a decreased incidence of 0.5% per year... the researchers reported in the June Arthritis & Rheumatism.
When applying the numbers to the total U.S. population, the researchers said the disease affects an estimated 1.5 million, up from a previously reported 1.3 million. The authors listed smoking rates, Vitamin D deficiencies and changes in oral contraceptives as the possible culprits behind the increase, and an accompanying editorial stressed the importance of further clarifying the reasons:
"Filling this knowledge gap will be critical in the design, implementation, and testing of public health interventions aimed at reducing the overall burden of RA," [Ted R. Mikuls, MD, of the University of Nebraska Medical Center, Omaha] wrote.
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