UCSF

Rationale & objective

In the general population, girls have lower mortality risk compared with boys. However, few studies have focused on sex differences in survival and in access to kidney transplantation among children with end-stage kidney disease.

Study design

Retrospective cohort study.

Setting & participants

Children aged 2 to 19 years registered in the US Renal Data System who started renal replacement therapy (RRT) between 1995 and 2011.

Predictor

Study participant sex.

Outcome

Time to death and time to kidney transplantation.

Analytical approach

We used adjusted Cox models to examine the association between sex and all-cause mortality. We used Fine-Gray models to examine the association between sex and kidney transplantation accounting for the competing risk for death.

Results

We included 14,024 children, of whom 1,880 died during a median 7.1 years of follow-up. In adjusted analyses, the HR for death was higher for girls (HR, 1.36; 95% CI, 1.25-1.50) than boys. When we further adjusted our survival models for transplantation as a time-dependent covariate, the hazard rate of death in girls was partially attenuated but remained statistically significantly higher than that for boys (HR, 1.28; 95% CI, 1.17-1.41). Girls were also less likely to receive a kidney transplant than boys (adjusted subdistribution HR, 0.91; 95% CI, 0.88-0.95) in analyses treating death as a competing risk.

Limitations

Lack of data for disease course before the onset of RRT and observational study data.

Conclusions

The mortality rate was substantially higher for girls than for boys treated with RRT. Access to transplantation was lower for girls than boys, but differences in transplantation access accounted for only a small proportion of the survival differences by sex.