Heart rate was also positively correlated with total AMS symptom score; in contrast, fluid intake was RNA Synthesis inhibitor negatively
correlated with total AMS symptom score. When investigating the symptom of high altitude headache alone (model 2 in Table 2), upper respiratory symptoms and stool consistency (where a higher number defines a looser stool) were correlated with headache severity, as did arterial oxygen saturation. However, when investigating presence or absence of clinically defined AMS (model 3 in Table 2), only upper respiratory symptoms (positive correlation) and arterial oxygen saturation (negative correlation) were significant predictors. Odds ratios suggested that a 1 unit increase in upper respiratory symptoms was associated with a 1.040 (1.005–1.262) significantly higher odds of having AMS; a 1 unit decrease in arterial oxygen saturation was associated with a 1.068 (1.000–1.141) significantly higher odds of having AMS. Time-lag models, which investigated whether variables predicted AMS the following day as required to infer causality, explained between 10 and 24% of variance in AMS (Table 3). The following day’s total AMS symptom score was positively correlated with upper respiratory symptoms (model 4 in Table 3). Heart rate and fluid intake also predicted future AMS symptoms. Thus, an increase of upper respiratory symptoms by 5 units
would increase total AMS symptom score the following day by 0.72 units (0.54–0.89); an increase in heart rate of 10 beats per min would
increase AMS score by 0.18 units (0.08–0.28); and a decrease of 10 mL per kg of body mass of fluid PFT�� chemical structure intake per day (∼710 mL per day) would increase total AMS score by 0.07 units (0.01–0.12). When investigating the symptom of high altitude headache alone, only arterial oxygen saturation was negatively correlated with the following day’s headache severity (model 5 in Table 3). Thus, a decrease in arterial oxygen saturation of 5% would increase headache severity HSP90 the next day by 0.06 units (0.02–0.10). This study is the first to use a longitudinal multiple regression analysis of daily illnesses and mental disturbances recorded during a relatively large expedition to high altitude. AMS affected almost half of the expedition participants, with up to one quarter having AMS on any day. However, AMS incidence alone underestimated the total illness symptom burden: all the participants also had upper respiratory symptoms, two thirds had loose stools and one third had diarrhea, and almost everyone reported mild anxiety. Upper respiratory symptoms increased as altitude was gained, and anxiety was also increased on certain days at high altitude. Detailed description of illnesses revealed that the variable contributing most to AMS symptom burden was difficulty sleeping. However, difficulty sleeping was also the least sensitive of the AMS symptoms to altitude change.