The effect of altitude on erythropoiesis-stimulating agent dose, hemoglobin level, and mortality in hemodialysis patients

Residence at higher altitude has been associated with improved anemia parameters and lower mortality rates among end-stage renal disease (ESRD) patients. However, these associations were observed prior to the 2011 shift in erythropoiesis-stimulating agent (ESA) dosing. To determine the impact of altitude on contemporary ESRD patients, a retrospective observational analysis was conducted in which patients were ascribed to one of four altitude categories as of 1 Jan 2012 and outcomes were assessed during 2012. Associations between altitude category and outcomes were estimated using generalized linear mixed models, adjusted for covariates that differed at baseline. Patients at higher altitude were less likely to receive ESA treatment, and dose was 723 U/treatment (95 % confidence interval [CI]: 544, 834) lower in the highest altitude category compared to the lowest category. The proportion of patients using IV iron decreased with increasing altitude category. Patients in the highest two categories had greater mean hemoglobin values (+0.15 and +0.23 g/dL) than the lowest. Mortality was lower for patients in the highest altitude category compared to those in the lowest (incidence rate ratio 0.73; 95 % CI: 0.63, 0.88), although their rate of missed dialysis treatments was slightly higher. This study confirms that, in the context of current anemia management practices, high altitude is associated with higher hemoglobin and lower mortality, despite lower utilization of ESA and IV iron.