Thanks to a tip from my friend Tod Schimelpfenig at WMI of NOLS (www.nols.edu), I checked out an article--available free if you type "High Altitude Medicine and Biology" into Google--entitled “Incidence and predictors of acute mountain sickness among trekkers on Mount Kilimanjaro.”
Kilimanjaro, the highest point on the African continent at a smidge over 19,300 feet, is notorious for altitude illness due to the rapid altitude gain it requires. Schedules and park fees apparently drive people to make the ascent from just about sea level in 5-6 days. While the study has some significant limitations, it showed a high rate of Acute Moutain Sickness (45%) and no protective effects from a mid-climb rest day or from acetazolamide. The study suggests, but does not prove, that you can go so high so fast that an occasional rest day or acetazolamide does not help.
The study also reports that a large number of climbers continue to ascend even though they have the signs and symptoms of AMS. You will also see, should you choose to read it, a reportedly and amazingly high rate of High Altitude Cerebral Edema (18%).
David Shlims, MD, long a doc for the Himalayan Rescue Association, gave the staff of WMI three, simple, golden rules for altitude at the WMI Staff Meeting in 2007:
1) If you feel unwell, it is altitude sickness until proven otherwise.
2) Never ascend if you have symptoms of altitude sickness.
3) If you are getting worse, then descend immediately.
Wise words indeed.