A new study to be published in the December 20/27 issue of
British Medical Journal presents results from the first detailed analysis of deaths during expeditions to the summit of Mt. Everest. Previous to the study, it was assumed that avalanche and falling ice, as well as pulmonary edema were the leading causes of death. The study found otherwise,
"High-altitude cerebral edema symptoms were common among those that
died, but signs of pulmonary edema, or excessive fluid in the lungs,
were unusual" Firth says. "We also were surprised at how few people
died due to avalanches and ice falls in recent years – those usually
happen at lower altitudes, and overwhelmingly people died during summit
bids above 8,000 feet – and that during descents, the mortality rate
for climbers was six time that of sherpas."
Read more about the study on causes of death on Everest.