The Influence of Sex on Rheumatoid Arthritis: a Prospective Study of Onset and Outcome After 2 Years

Objective: This prospective study analyzed influence of patient's sex on early rheumatoid arthritis (RA) within one year of disease onset and after 2 years' followup.

Methods: A total of 844 consecutive patients, 538 women, with RA of less than 12 months were studied. Standardized clinical and radiographic assessments were performed at study entry and after 2 years. The association of several variables at study entry with the outcome variables Disease Activity Score (DAS28), functional disability measured by the Health Assessment Questionnaire (HAQ), and, in 390 patients, Larsen score at the 2-year followup were analyzed in men and women separately.

Results: At study entry the women were younger compared with the men and the sexes showed different age distributions. The women had higher DAS28 and HAQ scores. However, women below 50 years of age at study entry had milder disease than older women and close to that of men. At 2-year followup the women still had higher DAS28 and HAQ scores compared to men, who had achieved remission in a higher frequency. Larsen score showed no sex difference either at study entry or after 2 years. Presence of rheumatoid factor (RF) was associated with lower age at study entry and higher DAS28 at followup in men only. Higher DAS28 and HAQ scores at entry were more strongly correlated with severe disease at followup in women than in men. Presence of the "shared epitope" was not associated with age or the outcome variables DAS28 and Larsen score in either sex.

Conclusion: The disease phenotype in early RA was significantly different between men and women, particularly concerning age, disease activity, and functional capacity. There were differences between the sexes concerning early disease characteristics associated with outcome at 2 years of followup.