Rheumatoid arthritis affects about one percent of the population, but it does affect women to a much greater extent than it affects men: the female to male ratio is approximately three to one. Age plays a role also: for women, the incidence of rheumatoid arthritis increases from puberty, peaking at menopause. Among men, rheumatoid arthritis is fairly rare before age 45.

In the October, 2006 issue of Arthritis and Rheumatism, the sex differences in rheumatoid arthritis were explored by...