Some research finds there may be differences in remission rates for men and women early in the course of rheumatoid arthritis, or RA. A recent study published online in Arthritis Care & Research found that men are more likely to achieve sustained remission– lasting for two or more doctor visits in a row – during the the first two years of having RA than women. But those gender differences don’t appear to last once patients have had the disease for more than two years.

“We found something. But what we don’t know is an awful lot about the whys and wherefores and what to do about them,” explains lead study author Daniel E. Furst, MD, a professor of medicine in the division of rheumatology at the University of California, Los Angeles, Medical Center.

The researchers analyzed data from 2,406 men and 7,893 women who were enrolled in the Consortium of Rheumatology Researchers of North America, or CORRONA, cohort between October 2001 and January 2010. The CORRONA network contains data submitted by 268 rheumatologists from 103 sites in 35 states for the purposes of prospective, observational research.

A total of 771 patients in this study achieved sustained RA remission – defined, according to the Clinical Disease Activity Index, as a patient having fewer than three tender and swollen joints, plus good marks on self-assessment and doctor-assessment questionnaires at two consecutive doctor visits that were two to six months apart.

After adjusting for certain factors that could skew results – such as disease severity at the time of enrollment, self-reported depression and work status – researchers learned that men had a 38 percent higher probability of attaining sustained remission in early RA than women. Early RA was defined as having had RA for fewer than two years.

“It’s a pretty striking finding since it took relatively few men to show that difference,” Dr. Furst explains.

Among the other findings: There was no gender difference in sustained remission rates among patients with established RA (having the disease for two years or longer). There was no gender difference when researchers looked at remission at one point in time, rather than over two doctor’s visits. And women had more severe disease activity than men in both early RA and established RA. The authors also acknowledge the gender differences they found are fairly small.

Dr. Furst says these findings help in the ongoing scientific effort to better understand why patients respond so differently to treatments. He says future research needs to confirm these results and search for explanations. He theorizes that differences could be explained by a variety of genetic, socioeconomic and physiological factors and it could even be that men and women perceive and/or describe their pain differently.

“We have to understand why women aren’t in remission as often and why they apparently aren’t responding as well to treatment as men,” Dr. Furst says. “If all of this turns out to be true, then we will treat women more aggressively, assuming no side effects, and help them have better long-term outcomes.”

Robert Katz, MD, a practicing rheumatologist at Rush University Medical Center in Chicago, says the small numbers in this study make the findings less than definitive. Also, he says, the way researchers defined remission involves a lot of subjective factors (especially pain and tenderness thresholds), noting that it’s not clear whether women have different pain perceptions than men, if their disease is actually different or if something as simple as dosing (men generally get more medicine since they weigh more) could be in play.

Still, he says, it is important to investigate the idea that gender, like ethnicity and age, could be a factor in a patient’s RA symptoms and response to treatment. He agrees the next important step is figuring out what accounts for the differences reflected in this study.  

“That’s an interesting thing that gender seems to play a role in the expression of RA and in the remission rates. But I don’t know if that reflects inherent gender differences relating to hormones or genetics, or if it reflects styles of receiving medical care and reporting pain and tenderness of joints,” Dr. Katz says.