Peter Rasmussen of the Zurich Center for Integrative Human Physiology at the University of Zurich, Switzerland, found short- or long-term use of EPO raised blood pressure by constricting arteries, which reduces the flow of blood to the brain.
Rasmussen and colleagues evaluated the effects of acute high doses of EPO for three days, and chronic low doses of EPO for 13 weeks, in two groups of healthy males.
Responsiveness of brain vessels during rest and during bike-riding exercise, with and without hypoxia -- low oxygen concentration -- was examined. Blood vessels were analyzed using ultrasound measurements and by measuring how much oxygen reached the brain.
The study, published by the journal of the Federation of the American Societies for Experimental Biology, found that prolonged EPO administration increased hematocrit -- the concentration of red blood cells in blood -- while acute administration did not. The study found both groups had increases in blood vessel constriction and higher blood pressure.
"EPO is used by doctors to increase red blood cells in sick people who can't make enough of them. When EPO is used by healthy bikers and runners to boost their performance, it's called cheating," said Dr. Gerald Weissmann, editor in chief of The FASEB Journal. "Now we know that folks who use EPO covertly are cheating not only the time-clock, but themselves. Not only is EPO likely unsafe in healthy athletes, but there are many other ways to build up stamina without drugs."