aIndependent samples t-test. bChi-squared test (2 2 contingency table, df = 1). indicated statistical significance. #Comparison of physiological parameters between baseline and measurements at 3700 m in all subjects. HAH+, subjects with HAH; HAH−, subjects without HAH. HAH, high-altitude headache; BMI, body mass index; HR, heart rate; SpO2, pulse oxygen saturation; SBP, systolic blood pressure; DBP, diastolic blood pressure.