Dialysis Patients Do Better at Higher Altitudes
A new study published in the Feb 4 issue of the Journal of the American Medical Association showed that patients on dialysis living at higher elevations do better than those residing at sea level.
Researchers had previously noted that individuals with end-stage renal disease who lived at higher altitudes achieved higher hemoglobin concentrations even while receiving lower doses of erythropoietin.
Hemoglobin is the protein in red blood cells that carries oxygen. Erythropoietin is a hormone that stimulates the production of more red blood cells (erythropoiesis).
Hypoxia-induced factors, whose activities may be increased at higher altitude in patients with ESRD, have been shown to improve iron availability which may lead to more efficient production of new red blood cells. Hypoxia-induced factors also regulate many enzymes that could affect cardiovascular risk.
This retrospective study followed more than 800,000 patients in the United States who started dialysis between 1995 and 2004 using data from the United States Renal Data System (USRDS).
After just under a year of follow-up, the mortality rate was 220.1 per 1,000 person-years at elevations under 250 feet; 221.2 at elevations of 250-1,999 feet; 214.6 between 2000 and 3,999 feet; 184.9 between 4,000 and 5,999 feet; and hit a low at 177.2 at altitudes above 6,000 feet.
That translated into a 15 percent reduced risk for those at the highest elevations compared to those at the lowest.
When the authors reviewed data from the U.S. Centers for Disease Control and Prevention they found that the general population also tends to live longer at a higher elevations. The difference is only half that seen in dialysis patients.
The authors suggest further study is needed as "We cannot be certain whether the observed association between altitude and mortality is causal." They say this after pointing out that one important limitation of the study is the possibility that their results could be due to uncontrolled patient characteristics or environmental factors correlated with altitude rather than an independent effect of altitude.
So don't go moving just yet.
The National Kidney Foundation has more on dialysis and kidney disease.
Altitude and All-Cause Mortality in Incident Dialysis Patients; JAMA, Feb 4, 2009, Vol 301, No 5, pp 508-512; Wolfgang C Winkelmayer, MD, ScD; Jun Liu, MD, MS; M Alan Brookhart PhD