To analyze sex difference in the effect of smoking on remission proportions in patients with rheumatoid arthritis (RA).
Subjects were Japanese patients with RA who participated in the IORRA survey conducted in April 2011 and reported smoking status. Clinical characteristics, treatment status, and the percentages achieving remission were compared between subjects stratified by sex and smoking status. To confirm the differential effects of sex and smoking status on remission, we used multivariate logistic regression models with the dependent variable as 28-joint Disease Activity Score (DAS28) remission.
Among 810 men and 4206 women, 162 (20.0%) and 3173 (75.4%), respectively, were never smokers; 208 (25.7%) and 314 (7.5%), respectively, were current smokers. In men, never smokers tended to have higher remission proportions than past and current smokers. In contrast, smoking status seemed not to affect remission in women. Except for lower corticosteroid dose in male never smokers, no significant differences were observed in comparing treatment status. By multivariate analyses, male past and current smokers were negatively associated with DAS28-erythrocyte sedimentation rate remission compared to male never smokers [OR 0.66 and 0.61, 95% CI (0.44-0.98) and (0.39-0.96), respectively]. However, female past and current smokers were not associated with remission compared to female never smokers [OR 1.04 and 1.19, 95% CI (0.86-1.25) and (0.91-1.54), respectively].
We demonstrated that the effect of smoking on remission proportions differed between men and women. Our findings suggest that both sex and smoking status are important considerations when planning a treatment strategy for patients with RA.