The epidemiological association of altitude with chronic kidney disease: Evidence of protective effect

Erythropoietin (EPO) exerts multiple positive functions, including possible slowing the progression of renal disease. It significantly attenuates interstitial fibrosis and reduces apoptotic cell death.1 As apoptotic cell death is a major contributor to chronic kidney disease (CKD) progression,2 it is plausible that, by reducing cell death, EPO might lead to slowing of the progression of CKD. Randomized studies in humans have shown that administration of EPO leads to slowing of CKD progression, and improves cumulative renal survival rate;3 a retrospective study has demonstrated that EPO administration is associated with significant delay in the need for dialysis.4 Furthermore, there is a well-defined relationship between altitude and EPO, which increases in response to low O2 at high altitudes. After 12 h of exposure to 2200 m, there is a significant increase (72%) of EPO above baseline.5 According to a study of 16 participants before and after 4 h of exposure to normobaric hypoxia during a 3-week altitude training (2100–2300 m), there is a wide inter-individual variability in erythropoietic response to altitude (10–185%).6 We hypothesize that residence at high altitude reduces the risk of CKD. The study consists of two objectives. Our first objective was to estimate the association between altitude of residence and estimated glomerular filtration rate (eGFR). Our second objective was to quantify the association between altitude and prevalence of end-stage renal disease (ESRD).