Prevalence of acute mountain sickness at 3500 m within and between families: a prospective cohort study.

AIM To investigate symptoms, prevalence and associated factors of acute mountain sickness (AMS) in families upon a fast ascent to 3450 m. METHODS 87 children, 70 adolescents, and 155 parents (n=312) were assessed for AMS 8-10 and 20-24 hours after fast passive ascent by the Lake Louise Score (LLS). Pain sensitivity and oxygen saturation (SO2) were measured and familial clustering was assessed. RESULTS AMS prevalence was significantly lower in children (21%) compared to adolescents (34%) and adults (39%) on day 1 (p<0.05), but not on day 2 (18% vs. 19% and 25%). Cumulative prevalence of AMS was 30, 37, and 45% in children, adolescents, and adults, respectively (p<0.001). Familial clustering of AMS was consistent and explained 25%-50% of variability in AMS. Pain sensitivity significantly increased from low to high altitude and was higher at low altitude in those with compared to those without AMS. SO2 at high altitude was not related to the presence of AMS. CONCLUSIONS After fast ascent to 3500 m, AMS prevalence was lower in children than in adolescents and adults on day 1, but not on day 2. Thus, children may travel at least as safely to an altitude of 3500 m as adolescents and adults, even if risk factors (pain sensitivity and heredity) are present.