Cardiovascular function in healthy Himalayan high-altitude dwellers

Area of Science:

• Cardiovascular Physiology
• High-Altitude Adaptation
• Vascular Biology

Background:

• Himalayan populations exhibit unique adaptations to chronic hypoxia, particularly in pulmonary vasculature.
• Systemic vascular function in high-altitude residents remains largely unexplored.
• This study investigates vascular function and structure in Sherpas at high altitude versus sea-level Caucasians.

Purpose of the Study:

• To investigate systemic vascular function and structure in a rural Sherpa population living at high altitude (HA) in Nepal.
• To compare vascular parameters between HA Sherpas and a control group (C) of Caucasian subjects living at sea level.

Main Methods:

• Enrolled 95 HA Sherpas and 64 Caucasian controls.
• Assessed cardiac ultrasound, brachial artery flow-mediated dilation (FMD), carotid artery geometry and stiffness, and aortic pulse wave velocity (PWV).
• Repeated FMD measurements in 11 HA subjects after 1-hour 100% oxygen administration.

Main Results:

• HA Sherpas demonstrated significantly lower FMD and hyperemic velocity compared to controls.
• HA Sherpas exhibited higher systolic pulmonary pressure but similar aortic PWV.
• Carotid intima-media thickness (IMT) was lower in HA Sherpas, with a larger diameter and increased wall stress.

Conclusions:

• High-altitude Sherpas exhibit reduced nitric oxide-mediated brachial artery dilation, linked to impaired microcirculation.
• A distinct carotid artery phenotype (reduced IMT, enlarged diameter) was observed in the HA population.
• Oxygen administration did not alter measured vascular parameters, suggesting chronic adaptive changes.