Sex-Dependent Association Between Early Morning Ambulatory Blood Pressure Variations and Acute Mountain Sickness

BACKGROUND: Acute high altitude (HA) exposure elicits blood pressure (BP) responses in most subjects, and some of them suffer from acute mountain sickness (AMS). However, a 24-h ambulatory BP (ABP) change and the correlation with the occurrence of AMS in different sexes are still unclear. OBJECTIVES: This prospective study aimed to investigate HA induced BP responses in males and females and the relationship between AMS and 24-h ABP. METHODS: Forty-six subjects were matched according to demographic parameters by propensity score matching with a ratio of 1:1. All the subjects were monitored by a 24-h ABP device; the measurement was one period of 24 h BP. 2018 Lake Louise questionnaire was used to evaluate AMS. RESULTS: Both the incidence of AMS (14 [60.9%] vs. 5 [21.7%], P = 0.007) and headache (18 [78.3%] vs. 8 [34.8%], P = 0.003) were higher in females than in males. All subjects showed an elevated BP in the early morning [morning systolic BP (SBP), 114.72 ± 13.57 vs. 120.67 ± 11.10, P = 0.013]. The elevation of morning SBP variation was more significant in females than in males (11.95 ± 13.19 vs. −0.05 ± 14.49, P = 0.005), and a higher morning BP surge increase (4.69 ± 18.09 vs. −9.66 ± 16.96, P = 0.005) was observed after acute HA exposure in the female group. The increase of morning SBP was associated with AMS occurrence (R = 0.662, P < 0.001) and AMS score (R = 0.664, P = 0.001). Among the AMS symptoms, we further revealed that the incidence (R = 0.786, P < 0.001) and the severity of headache (R = 0.864, P < 0.001) are closely correlated to morning SBP. CONCLUSIONS: Our study demonstrates that females are more likely to suffer from AMS than males. AMS is closely associated with elevated BP in the early morning period, which may be correlated to higher headache incidence in subjects with higher morning SBP.