Epidemiological aspects of rheumatoid arthritis: the sex ratio

Many rheumatic diseases, including rheumatoid arthritis (RA) are more frequent in females than males. The objective of this article was to examine the female versus male perspective regarding prevalence/incidence, etiological factors, disease severity/outcomes, access to therapy and therapeutic responses. We also present results from some new analyses from the patient registers in Oslo to supplement existing literature in this area. We found that the prevalence of RA is higher in females than males, the incidence is 4-5 times higher below the age of 50, but above 60-70 years the female/male ratio is only about 2. Smoking is a consistent predictor of RA in males, but findings have been more inconsistent in females. We could not confirm that health status is worse in females than males when corrections were made for different disease duration and for the underlying tendency of healthy females to report worse subjective health status than males. Some studies and data presented here indicate that females have less access to health services. We also found that female sex reduces the likelihood of achieving treatment response with methotrexate and anti-tumor necrosis factor (anti-TNF) drugs by 30-50%. More research is needed to fully describe the differences between males and females regarding epidemiological data.