Altitude tied to kidney health

Dialysis patients who live at higher altitudes survive severe kidney disease better than patients living at lower elevations, thanks to changes in the body at greater elevations, researchers report.

Compared to patients living close to sea level, those at elevations of 1 200 to 1 800 metres have a 12% better survival rate after five years, and those above 1 800 metres have a 15% better rate, the researchers said.

Johannesburg is 1 750 metres above sea level and Bloemfontein is 1 400.

Rates rose steadily
In fact, survival rates for patients with end-stage kidney disease who have dialysis rose steadily as the altitude of where they lived increased, the researchers wrote in the Journal of the American Medical Association.

Dialysis treatment does some things that a failing kidney no longer can do. These include removing waste, salt and extra water from the body, maintaining safe levels of certain chemicals in the blood and helping control blood pressure.

"The prognosis once you have end-stage renal disease and require dialysis is really grim. It compares to having certain types of cancer," Dr Wolfgang Winkelmayer of Brigham and Women's Hospital and Harvard Medical School in Boston, who led the study, said in a telephone interview.

"Once a person reaches end-stage renal disease, the only treatment options are either to undergo dialysis or kidney transplant," Winkelmayer said.

How the study was conducted
The researchers examined data on 804 812 US dialysis patients, establishing their altitude by using their postal code.

A previous study found that dialysis patients living at higher altitudes responded better to treatment using a protein called erythropoietin that controls red blood cell production.

Hypoxia, an oxygen deficiency in the blood that occurs at higher elevations, may make erythropoietin more effective, the researchers said. There also could be other benefits of mild hypoxia for patients undergoing dialysis, they added.

(Reuters Health, February 2009)