24 - 30 October 2014 #729

In the genes

What makes Sherpas physiologically well-adapted to perform arduous tasks in the mountains?
Dhanvantari by Buddha Basnyat, MD

When news broke of the fist fight between Sherpa guides and three international Alpine-style climbers on Mount Everest last year, many were left astounded. After all, violence was something that the world didn’t associate with Sherpas, the mountain community known for their friendly and helpful nature. Different versions of the event debating how and why the brawl happened and what this would mean for the future of mountaineering and tourism in Nepal emerged in the media soon after.

Every spring season, the high altitude guides fix ropes, set up camps and pave the way for less experienced climbers to summit Mount Everest. The rescue teams that performed “long line” high altitude rescues in the Annapurna and Dhaulagiri regions of the Himalayas in the wake of last week’s blizzards were comprised mainly of Sherpas.

This column will not extend on that debate further but look into what makes Sherpas physiologically well-adapted to performing arduous tasks like fixing ropes at high altitudes.

There is a sharp contrast in the adaptive mechanism between high altitude Tibetan (from whom the Sherpa people derive their ancestry) population and the recently-settled Han Chinese population in the Tibetan plateau. Tibetan women have generally uncomplicated pregnancies compared to the relatively complication-ridden pregnancies of the Han Chinese women. In fact this problem is so acute that most expectant Han Chinese women move to lower altitudes during the course of their pregnancy for safer delivery.

It seems people of Tibetan origin are better adapted to hypoxia (low oxygen) even before their birth. Infants born to Han Chinese parents may have pulmonary hypertension (increased blood pressure in the blood vessels of the lungs) leading to heart failure. This condition is seldom seen in a newborn Tibetan infant. Even if a Han Chinese infant survives childhood, she finds herself at a greater chance to suffer from chronic mountain sickness (CMS). CMS is rarely seen in Tibetans.

As opposed to acute mountain sickness (AMS) which is regularly seen in the Nepal Himalayas, CMS is characterised by excessive red blood cells and leads to heart failure and strokes due to ‘sludging’ in the circulation of blood. CMS is also common among the high mountain dwellers of South America.

From intrauterine life to infancy to adulthood, Tibetans seem to have a protective mechanism that helps them cope with altitude. The natural ability to adapt in high altitude when combined with training makes them able to perform difficult tasks like putting up ropes, setting up camps, and other exertion-related work better at high altitude areas.

These physiological findings have been corroborated by the molecular discovery of the potentially protective hypoxia inducible factor (HIF) gene by Peter Ratcliff and Greg Semenza. A flurry of medical reports has revealed people with Tibetans ancestry possess the HIF gene, but not the Han Chinese. No wonder the Sherpas are agile in helping people whether it is for guiding or rescue operations in the Himalayas.

Read also:

Step by step, Buddha Basnyat

Mastering the mountains, Buddha Basnyat

Your pulse in your hands, Buddha Basnyat

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