Abstract
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There are at least two factors responsible for this change. One is the extensive movement of Han Chinese into the Tibet autonomous region. The Tibetan plateau has an area of about 2,500,000 square km or 970,000 square miles with an average elevation stated to exceed 4500 m. Many inhabited areas are at altitudes over 4000 m and, in general, Han Chinese do not tolerate high altitude well. As a consequence there is a tremendous interest in high altitude diseases, particularly acute mountain sickness (AMS). For example there have been many studies of the incidence of AMS in Chinese soldiers airlifted to Lhasa or other parts of Tibet.
A particularly challenging project was constructing the railway from Golmud in Qinghai province to Lhasa. The track reaches an altitude of over 5000 m, and one of the tunnels through a mountain is at the punishing altitude of 4900 m. This project was a gigantic undertaking and, as expected, was associated with many cases of AMS, and apparently some of high altitude pulmonary edema and high altitude cerebral edema as well.
Another reason for the expanding research program is the accelerating interest in the biology of Tibetans who have lived for many centuries at these high altitudes. Again this is a relatively new interest. By contrast there is a long history of research on the permanent residents of high altitude in the South American Andes. Here a critical figure was Carlos Monge Medrano (1884–1970) who lived in Lima but who developed a pioneering interest in the permanent residents of high altitude Peru. For example his ground-breaking book “La enfermedad de los Andes,” which contained the first description of chronic mountain sickness (also known as Monge's disease), was published in 1928. But his most influential publication was “Acclimatization in the Andes: Historical Confirmations of ‘Climatic Aggression’ in the Development of Andean Man,” which appeared in 1948. There he proposed that permanent residents of high altitude in Peru were fundamentally different from sea-level man, arguing that the “biological personality” of Andean man “must be measured with a scale distinct from that applied to the men of the lower valleys and plains.” This provocative statement has not been generally accepted although recent genetic studies perhaps add credence to it. Incidentally the only other area of the world where there is a substantial population of permanent residents at high altitude is in the Ethiopian highlands, but this group has attracted limited attention so far.
One of the most interesting developments of the past few years has been the discovery of genetic differences in Tibetans compared to Han Chinese. For example it has been shown that Tibetans have overrepresentation of variants in the EPAS1 gene that encodes for hypoxia-inducible factor 2α (HIF-2α). Hypoxia-inducible factors are transcription factors that constitute a master switch controlling a large number of genes that are upregulated or downregulated by hypoxia, and the result is a wide range of physiological responses. A striking recent finding is that some of these genetic characteristics may stem from those of Denisovan hominids who were contemporaries of the Neanderthals.
These exciting developments are changing the face of many aspects of high altitude medicine and biology. Nevertheless it might be added that there are some worrying aspects of this flourishing research in China. One is the severe restrictions on materials such as tissue samples and DNA that can be taken out of China. This negative attitude has had some bizarre results including the fact that some researchers have found it easier to collect material from Tibetans living in San Francisco or London rather than going to China. Although this is an ingenious workaround strategy, it clearly impedes progress in this field. The Chinese government also imposes other curious restrictions. For example YouTube is not accessible in China. To many of us this seems to be a severe and unnecessary penalty since so much useful information is now available on this platform.
Having said this, the explosion of research in high altitude medicine and biology in China is certainly a very welcome development and we look forward to increasing expansion of knowledge in this fascinating area.