Sex Differences & Rheumatoid Arthritis

Despite statistically significant differences in the values between men and women, the effect sizes of these measures were limited and smallest for the swollen joint count, which was then used as an objective surrogate for inflammation. Among patients who had minimal disease activity in terms of joint swelling (i.e., no swollen joints or only one), women had statistically significantly higher mean values compared with men in all other disease activity measures (p<0.001) and met DAS28 remission criteria less frequently than men.³⁵ Similar proportions of females and males were taking the various therapies. Rheumatoid factor was equally prevalent among genders. Men had nodules more often than women. Women had erosions more often than men, but the statistical significance was marginal, echoing data from other studies with similar radiographic progression in women and men.^36–38

The QUEST-RA data show that currently used disease-activity measures indicate higher activity in women than in men. The higher likelihood of remission in men versus women according to DAS28 can be explained in large part by the observation that higher values for all DAS28 components were seen in women.³³ Indeed, most people over age 50 years in the general population who do not have RA do not meet the ACR remission criteria for RA—women less often than men.³⁹ Disease severity was similar between sexes with respect to the proportion of women and men with an erosive disease; in addition, from what is known about long-term outcomes from longitudinal cohorts, it appears that most gender differences in RA disease activity may result from characteristics of the measures of disease activity, rather than from RA disease activity itself.

Explaining Other Sex Differences

At present, a “gold standard” for RA disease activity does not exist. Furthermore, the currently used disease-activity measures may reflect phenomena other than those associated with RA, which may lead men to have better scores. Several reports indicate that women with RA report more severe symptoms, greater disability, and higher work disability rates compared with men.^40-42 Women report poorer scores than men for daily physical activities; this finding is understandable because women have less strength than men.^{40,41;43–48} In fact, the sex differences in musculoskeletal performance remain even among the most physically fit, best-trained individuals. After all, female and male athletes compete separately.

It is of particular interest that gender differences for DAS28, fatigue, and RA Core Data Set measures were most pronounced in patients with low swollen joint counts in the QUEST-RA study. This finding can be interpreted to suggest that, even at minor disease activity levels, the burden of the disease is greater for women than for men, or that women are more likely than men to report problems. Concerning musculoskeletal size and strength, women’s baseline values are lower than men’s. Therefore, the same severity of a musculoskeletal disease may be reported as a problem more often by women than men.