Serious Altitude Illness in Travelers Who Visited a Pre-Travel Clinic

Background. Few data are available on the incidence and predictors of serious altitude illness in travelers who visit pre-travel clinics. Travel health consultants advise on measures to be taken in case of serious altitude illness but it is not clear if travelers adhere to these recommendations. Methods. Visitors to six travel clinics who planned to travel to an altitude of >= 3,000m were asked to complete a diary from the first day at 2,000m until 3 days after reaching the maximum sleeping altitude. Serious altitude illness was defined as having symptoms of serious acute mountain sickness (AMS score >= 6) and/or cerebral edema and/or pulmonary edema. Results. The incidence of serious altitude illness in the 401 included participants of whom 90% reached >= 4,000 m, was 35%; 23% had symptoms of serious AMS, 25% symptoms of cerebral edema, and 13% symptoms of pulmonary edema. Independent predictors were young age, the occurrence of dark urine, travel in South America or Africa, and lack of acclimatization between 1,000 and 2,500 m. Acetazolamide was brought along by 77% of the responders of whom 41% took at least one dose. Of those with serious altitude illness, 57% had taken at least one dose of acetazolamide, 20% descended below 2,500m on the same day or the next, and 11% consulted a physician. Conclusions. Serious altitude illness was a very frequent problem in travelers who visited pre-travel clinics. Young age, dark urine, travel in South America or Africa, and lack of acclimatization nights at moderate altitude were independent predictors. Furthermore, we found that seriously ill travelers seldom followed the advice to descend and to visit a physician.