Acute mountain sickness (headache, nausea, dizziness, fatigue and insomnia) is caused by the lack of oxygen at higher altitudes according to the National Institutes of Health.
Not everyone is affected by altitude, but among visitors to Colorado’s ski areas the incidence is 22% at 8,000 feet and 40% at 10,000 feet. The higher you go the worse it gets. Of those staying at 7,000 to 9,000 feet 22% experienced Acute Mountain Sickness while at 10,000 feet, the incidence rose to 42% according to medical studies cited an article by Dr. Peter Hackett and Dr. Robert Roach of the University of Colorado Altitude Research Center and published in The New England Journal of Medicine in July 2001.
What we do know clearly from multiple studies is that getting altitude sick varies from time to time and from person to person. One person may get altitude sickness while his equally healthy and fit buddy does not. You may not have gotten altitude sick on previous visits to Colorado but you may get it on the next trip.
We are all susceptible to Acute Mountain Sickness. Whether a person is a child or adult, male or female, fit or out of shape doesn’t seem to make a significant difference, said Dr. Rob Roach, now director of the Altitude Research Center at the University of Colorado. It’s impossible to predict who will be affected though research is being done in this area.