HMN 2025: How Acute mountain sickness is associated with blood flow changes

Acute mountain sickness (AMS) is common at high altitudes and is often associated with headaches. AMS is theorized to be caused by changes in cerebral blood flow, but this phenomenon is still not well understood. Although past studies addressing AMS have been conducted, none were for sufficient durations and in actual high-altitude environments.

To fill this gap in AMS research, Professor Kazunobu Okazaki’s team at the Osaka Metropolitan University Research Center for Urban Health and Sports measured blood flow and vessel diameter in the internal carotid and vertebral arteries in eight healthy men at the 3,776-meter summit of Mount Fuji for three days. Simultaneously, the team scored symptoms of altitude sickness, such as headaches and fatigue.

Results showed that blood flow and vessel diameter in the internal carotid artery increased with the length of stay, whereas flow in the vertebral artery increased during the first day, but decreased afterward. A clear correlation was observed between headache intensity and changes in blood flow.

“These findings shed light on one mechanism behind altitude sickness onset and can possibly aid in managing climbers’ physical conditions during mountain hikes and high-altitude training,” stated Professor Okazaki, first author of the study published in the Journal of Applied Physiology.

“We believe that further investigation into individual differences, gender differences, and the acclimatization process during long-term stays will yield insights applicable to the prevention and early management of altitude sickness. In addition, the relationship between cerebral blood flow and headaches may also contribute to understanding other headache disorders, such as migraines.”

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