Sex differences in clinical outcomes in Japanese incident dialysis patients: a prospective observational multicenter study

Background: A Dialysis Outcomes and Practice Patterns Study (DOPPS) has shown a one-to-one male-to-female mortality ratio, notwithstanding the statistically longer life expectancy of women in the general population. This finding contrasts with the recent report that Japanese women on dialysis treatment have a more favorable longevity. Accordingly, we further investigated the clinical procedures and outcomes to clarify the sex differences in Japanese patients undergoing dialysis treatment. Methods: Subjects were incident dialysis patients who participated in a multicenter prospective cohort study from October 2011 to September 2013. The all-cause mortality was analyzed by a Cox proportional hazard regression model and studied separately in women and men with or without cardiovascular disease (CVD) at baseline. Results: Overall, 492 (32.3%) of the 1520 test subjects were women. All-cause mortality was higher in men (28.6%) than in women (19.9%, p < 0.001). Female sex (hazard ratio [HR]: 0.70, 95% confidence interval [CI]: 0.54–0.90) and history of CVD (HR: 1.51, 95% CI: 1.18–1.95) were independent predictors of all-cause mortality. In patients without CVD, female gender was strong independent contributor (HR = 0.46, 95% CI: 0.30–0.70, p < 0.001). In contrast, patients with CVD showed no difference in survival between the sexes (HR: 0.92, 95% CI: 0.67–1.24, p = 0.597). Conclusion: Our study demonstrated that women undergoing chronic dialysis therapy had a lower mortality risk than men. However, complication with CVD canceled out the survival advantage in Japanese women on chronic dialysis. We should reevaluate the risk of women with CVD undergoing dialysis and apply the optimal care for CVD.