203), nor between AMS incidence and reading or understanding the written information (p = 0.942 and 0.500, respectively). Logistic regression analysis identified all these variables except the average increase in altitude as independently significant (Table 4). Travelers who experienced Kinase Inhibitor Library screening AMS on a previous journey were twice more likely to develop AMS. The risk for women was 1.5 times higher than for men, and the risk decreased with an OR of 0.984 for every year of age. The risk increased with an OR of 1.2 for every 500 m increase in maximum overnight altitude and it decreased with

an OR of 0.9 for every night that was spent between 1,500 and 2,500 m at the beginning of the journey. We found no relation between acetazolamide prevention and AMS selleck compound (p = 0.540) in this population, nor in the subgroup (N = 66) of those with a prior history of AMS (p = 0.787); but this sample has insufficient power for conclusions of absence of effect. In those with previous AMS, there

were no more risk factors in the subgroup of travelers who took acetazolamide preventively than in those who did not. Thus, mean-maximum altitude (p = 0.134), mean number of nights spent between 1,500 and 2,500 m (p = 0.151), and mean age (p = 0.759) were the same in both subgroups, which contained an equal number of women and men (p = 0.258). Nor was there a relation between acetazolamide treatment and the duration of AMS complaints (p = 0.169). Eleven percent reported an increased urine production and 30% reported side effects, of which a tingling sensation in hands and feet was the most common (25%), followed by gastrointestinal complaints (5%), headache (2%), taste alteration, muscle cramps, and coughing (each 1%). We found no relation between dosage and

the side effects (p = 0.336). This study shows that 25% of travelers who consulted our pre-travel clinics for a journey to an altitude above 2,500 TCL m developed AMS. Predictors were previous AMS, gender, age, maximum overnight altitude, and number of nights between 1,500 and 2,500 m. No more than about half of these travelers followed our advice regarding prevention and treatment. We found no effect of acetazolamide on AMS incidence or the duration of AMS complaints. We found an AMS incidence of 13% between 2,500 and 3,000 m, while Mairer found an incidence of 17% at an altitude of 2,800 m in trekkers in the Eastern Alps.14 They found an incidence of 38% at 3,500 m, compared with 22% between 3,500 and 4,000 m in our study. Wagner found 43% at 4,500 m on Mount Whitney, compared with 30% between 4,500 and 5,000 m in our study.15 Mairer and Wagner also used the Lake Louise definition on altitude illness, but added that the total score of symptoms had to be at least 3 (Wagner) or 4 (Mairer). As we did not use scores, we would have expected a higher incidence in our study.