Dialysis Patients Living at Higher Altitudes Have a Lower Rate of Death

Dialysis patients living at altitudes higher than 1,200 meters have a 12-15% lower rate of death compared to those living near sea level, according to a new study.

Researchers at Brigham and Women's Hospital (Boston, MA, USA) examined a comprehensive U.S. dialysis registry and identified 804,812 patients with end stage renal disease (ESRD) who initiated dialysis between 1995 and 2004, and who met the study entry requirements. Most patients resided below an altitude of 75 meters (40.5%) or between 75-610 meters (54.4%). Only 1.9% of incident dialysis patients lived between 1,200 and 1,800 meters, and 0.4% lived higher than 1,800 meters. Patients were stratified by the average elevation of their residential U.S. postal (zip) code.

The results showed that when compared with patients living at lower altitudes, the rate of death was reduced for patients living from 75-610 meters by 3%; from 600 to 1,200 meters by 7%; from 1,200 and 1,800 meters by 12% percent; and higher than 1,800 meters by 15%. Actuarial 5-year survival was 34.8% for patients living at or near sea level but was 42.7% among those living at an altitude higher than 1,800 meters. Patients in the highest elevation group experienced a 7.9% greater absolute or 22.7% greater relative 5-year survival. Median (midpoint) survival after initiation of dialysis was 3.1 years for those living lower than 75 meters, but was four years for those living at an altitude higher than 1,800 meters, a difference in median survival of 0.9 years between the two groups. While a decrease in age- and sex-standardized mortality at higher altitude was also observed in the general population, the magnitude of the risk reduction was half of that observed in the ESRD population. The study was published in the February 4, 2009, issue of the Journal of the American Medical Association (JAMA).

"…We found a graded reduction in mortality from any cause in ESRD patients residing at greater altitude, a finding that was not explained by differences in observed patient characteristics,” concluded lead author Wolfgang Winkelmayer, M.D., Sc.D., and colleagues. "The magnitude of this observation was markedly greater than the observed small reduction in mortality at higher altitude in the general population. We propose that hypoxia-inducible factors are persistent at high altitude in patients with ESRD and may confer protective effects.”

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