LUND, Sweden, Dec. 14 -- Men are more likely than women to achieve rheumatoid arthritis remission, researchers here have found.

In the study of 698 patients with early RA, gender appeared to be the most important predictor of remission, reported Björn Svensson, M.D., of the University Hospital, and colleagues, online in the Annals of the Rheumatic Diseases.

After two years, 32.1% of women compared with 48% of men had achieved remission, defined as a disease activity score (DAS28) of less than 2.6, (P=0.001), though their disease characteristics were not significantly different at baseline.

After five years, the difference in remission was even more pronounced (30.8% of women versus 52.4% of men, P=0.001). The number achieving remission at both time points was 19.1% for women and 39.3% for men (P=0.001).

The odds ratios for sex as a predictor of remission remained significant when sex, disease duration and an interaction term for the two were included in multiple logistic regression analyses. Male sex was the strongest independent predictor of remission at all time points. The odds ratios were:

• 1.557 at 18 months (95% confidence interval 1.062 to 2.283, P=0.023),
• 1.713 at 24 months (95% CI 1.208 to 2.431, P=0.003),
• 2.837 at 60 months (95% CI 1.905 to 4.224), and
• 2.641 for all three time points (95% CI 1.632 to 4.273).

The multicenter study included Swedish patients with disease duration of about one year according to 1987 American College of Radiology criteria. Patients were assessed at baseline and at three, six, 12, 18, 24 and 60 months.

Among the participants (mean age 58 at inclusion, 64% female), 77% had moderate or severe disease activity, 56% were positive for antibodies to cyclic citrullinated peptide, and 60% were positive for rheumatoid factor. At baseline, disease characteristics for the sexes were similar overall. The findings were (women versus men):

• Higher mean DAS28 scores for women (5.37 versus 5.09, P=0.005).
• A slightly higher mean pain scores among women (47 versus 43, P=0.027).
• C-reactive protein levels were higher among men (18 versus 27, P=0.001).
• No significant difference in morning stiffness (128 versus 121, P=0.43).
• No significant difference in Signals of Functional Impairment (SOFI) index physical performance scores (8 versus 9, P=0.11).

At the 24-month assessment, 261 of 689 patients were in remission (37.9%). At the 60-month assessment, the remission rate was 38.5%. Only 26.1% were in remission at both time points.

For women compared with men, the frequency of remission was (P=0.001 for all):

• 30.4% versus 41.7% at 18 months.
• 32.1% versus 48.0% at 24 months.
• 30.8% versus 52.4% at 60 months.

For women versus men, period remission, defined as remission at two or more consecutive time points, was:

• 22.1% versus 33.8% at 18 and 24 months (P=0.002).
• 19.1% versus 39.3% at 24 and 60 months (P=0.001).
• 13.8% versus 30.3% at 18, 24, and 60 months (P=0.001).

Disease course also seemed worse among women. DAS28 scores were significantly less improved by treatment than men at the two-year follow-up (mean change 21.96 versus 22.32, P=0.001) and five-year follow-up (mean change 21.92 versus 22.32, P=0.001). Pain and morning stiffness tended to be higher in women as well. HAQ scores for difficulty in activities of daily living were significantly greater for women at the two- (0.69 versus 0.47, P=0.001) and five-year follow-ups (0.69 versus 0.47, P=0.001).

The researchers said the reasons for the difference in remission rates between the sexes were unclear and not explained by differences in disease duration, age, or treatment with DMARDs or glucocorticoids.

Both groups received comparable treatment during the study period. At baseline, 39% of women and 37% of men were on methotrexate, 34% of both groups were on sulfasalazine, and 12% of both were on other disease modifying antirheumatic drug (DMARD) monotherapy. At two and five years, the percentages were still similar between groups for types of therapy. At baseline, 42% versus 41% were given prednisolone, which decreased to 35% versus 33% at two years and 23% versus 17% at five years. Mean daily doses were not significantly different at any time point (P=0.30 at baseline, P=0.33 at two years, and P=0.77 at five years).

However, they concluded that "the data seem solid enough to call for reinforced vigilance in the frequency and quality of follow-up to achieve optimum suppression of the inflammatory process of all patients, regardless of sex."

The study was supported by grants from The Swedish Rheumatism Association, King Gustaf V 80 year's Foundation, the Gorthon Foundation, and Stiftelsen för Rörelsehindrade i Skåne. The authors declared no competing interests.