Effect of short-term high-altitude acclimatization on the relationship between cerebral blood flow and symptoms of mild acute mountain sickness in males.

People who climb high altitudes frequently experience headaches, which are the primary symptoms of acute mountain sickness (AMS). Although headaches and AMS are primarily caused by hypoxia, they remain poorly understood, specifically, the effects of regional cerebral blood flow on headache and AMS. In this high-altitude laboratory study, we investigated the hypothesis that regional cerebrovascular responses to high-altitude (3,776 m) sojourns are associated with AMS symptoms. The internal carotid artery (ICA), vertebral artery (VA), cardiorespiratory and vascular responses, and symptoms of AMS were assessed in eight healthy male lowlanders (mean age, 34 yr) at sea level (SL, 450 m) and on three consecutive days at the summit of Mount Fuji (3,776 m). Compared with sea level, ICA flow increased on day 3 (P = 0.009) and ICA diameter increased on days 1-3 (P < 0.001). In contrast, VA flow increased on days 1 and 2 (P = 0.008 and P = 0.018, respectively) and VA velocity increased on day 1 (P = 0.044). Headaches increased over the 3 days (P = 0.011 to P = 0.048), but AMS increased on day 3 (P = 0.001). Repeated-measures correlation analysis revealed that changes in headaches from the previous day were correlated with percent changes in ICA diameter (rrm = 0.596, P = 0.012), VA flow, and velocity (rrm = 0.537, P = 0.026 and rrm = 0.619, P = 0.008, respectively). Thus, a high-altitude-induced increase in cerebrovascular perfusion may contribute to the worsening of headaches, which is a typical AMS pathogenesis.NEW & NOTEWORTHY Acute mountain sickness (AMS) symptoms for 3 days at 3,776 m were assessed using volumetric cerebral blood flow. Internal carotid arterial (ICA) flow increased gradually, whereas vertebral arterial (VA) flow acutely increased on day 1 but decreased thereafter. Headaches increased over 3 days, but AMS did not until day 3. Changes in headaches were correlated with those in ICA diameter and VA flow/velocity. Thus, a high-altitude-induced increase in cerebrovascular perfusion may contribute to worsening headaches.