Tibetan children who grow faster than other children up to the age of five presumably do so as a defense against heat loss since larger bodies have a more favorable surface to volume ratio. Recently scientists have been trying to isolate the cultural and genetic factors behind the ability to adapt and to survive extremes of altitude and cold, of which Tibetans have a legendary reputation conditioned by the extreme environment of the Tibetan plateau and they have discovered a gene which improves oxygen saturation in hemoglobin.

One of the villages is in a mountainous area 1000 metres above sea level; the other two are on the plains. The livelihoods in all three villages are similar - farming and animal husbandry for the men and housework for the women. Overall, both men and women living in the mountain village had higher rates of circulating blood lipids and higher blood pressure and a worse coronary heart disease risk profile than their peers living in the lowland area.

In 1996 the researchers assessed the number of survivors over the 15 years, 150 men and 140 women died. Of these, 67 deaths, 34 of which were among the men, were attributable to coronary heart disease; after taking account of all the cardiovascular risk factors, mountain village residents had lower death rates, and lower rates of death from heart disease, than their peers in the lowlands and this was more so among the men.

The conclusion reached was that other 'protective factors' must be in action as blood lipids and blood pressure were higher among the mountain residents. It appears that living at moderately high altitude produces long term physiological changes in the body enabling it to cope with lower levels of oxygen, and this, along with the exertion required to walk uphill regularly on rugged terrain, could give the heart a better work-out.

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