Even if genetic factors certainly have an important role, at the basis of the incidence and prevalence of rheumatoid arthritis, no doubt, there are other factors. In order to verify the extent of this disease, some researchers at Mayo Clinic have examined the data relative to cases of rheumatoid arthritis diagnosed in Olmsted, Minnesota, between 1995 and 2007. A slight increase in the disease during this period, but only in women, was found: many hypotheses have been developed to explain this datum, hypothesizing a decrease in smoke, a greater vitamin D deficiency, a greater use of oral contraceptives with low estrogen amounts (estrogens have a protective role towards rheumatoid arthritis onset) in women, even if a definitive word has not been said yet and, no doubt, other factors intervene in the genesis of this disease.
According to the results of this limited analysis, the incidence of rheumatoid arthritis is not at all declining, as it has been affirmed on many occasions; on the contrary, in women, there would be a slight increase, even if we are still far from understanding the reason.
