• headache;
  • high altitude;
  • aspirin;
  • prophylaxis;
  • exercise;
  • mountaineering

Objective.—To evaluate the efficacy of aspirin for headache when exercising during acute high-altitude exposure.

Background.—Aspirin effectively prevents headache when mostly resting during acute high-altitude exposure. However, the majority of individuals exposed to high altitude perform mountaineering activities, which might trigger headache.

Design.—Randomized, double-blind, placebo-controlled trial.

Methods.—Thirty-one healthy volunteers (20 men, 11 women; aged 22 to 59 years) were transported to an altitude of about 3000 meters and climbed up to 3800 meters. They then descended to a mountain hut at 3480 meters and spent 2 nights there. Tablets (placebo or 320 mg aspirin) were administered three times at 4-hour intervals, beginning 2 hours before arrival at high altitude. Headache scoring and measurements of heart rate, blood pressure, and arterial oxygen saturation were performed.

Results.—Ninety-three percent (14 of 15) of the placebo group and 56% (9 of 16) of the aspirin group developed headache when mountaineering activities were performed during acute exposure to high altitude (P<.05). Five hours after arrival at high altitude, mean resting oxygen saturation was 86.1% ±  2.1% with aspirin and 85.7 % ±  2.8% with placebo (P = .66). However, subjects in the aspirin group developed headache at saturation values less than or equal to 86%, while those in the placebo group developed headache at saturation values less than 90%.

Conclusions.—Although the prophylactic intake of about 1 gram of aspirin reduced the headache incidence when exercising during acute high-altitude exposure, the incidence of headache was higher than previously shown for resting conditions. Aspirin resulted in tolerance to lower arterial oxygen saturation without development of headache; exercise had the opposite effect.