Editorial: Exciting times in the study of permanent residents of high altitude (p. 1)

These are heady times for scientists interested in the evolution of people who have successfully adapted to permanent residence at high altitude. Landmark studies of the genetic difference between Tibetans and Han Chinese have been published, and one of the most provocative assertions is that the two populations may have diverged in less than 3,000 years. If true this would probably be the most rapid example of Darwinian natural selection that has ever been observed in humans. Another fascinating issue is the phenotypical differences between Andeans and Tibetans. It is extraordinary that these two populations that have successfully adapted to the severe hypoxia of high altitude should have reached such different solutions.

Sightings, edited by John W. Severinghaus (p. 5)

High Altitude Web, edited by Thomas E. Dietz (p. 9)

Clinician's Corner, edited by Andrew Luks (p. 13)

How do you approach seizures in the high altitude traveler?

Maa (p. 13) tackles the difficult problem of how to advise patients who develop first-time or breakthrough seizures at high altitude. There is little published guidance on this knotty topic.

Pro and Con, edited by Erik R. Swenson (p. 21)

This is a new feature that will air controversial topics in high altitude medicine and biology. The first topic is, “Should headache be a required symptom for the diagnosis of acute mountain sickness?” The pro side is taken by Roach, Hackett, and Kayser (p. 21) and the con side by West (p. 23). Following the initial statements each side was allowed a short rebuttal. Readers are invited to add their comments as Letters to the Editor.

Scientific Articles

Positive association between altitude and suicide in 2584 U.S. counties

Brenner (p. 31) reports on an unexpected and so far unexplained association between residence at high altitude and the risk of suicide. The authors controlled for known suicide risk factors including age, gender, race and income.

Minimal effects on human memory following long-term living at high altitude

Zhang and colleagues (p. 37) noted that although it is known that memory is impaired at extremely high altitude, there is little data about the effects of long term living on memory at moderate altitudes. They studied 52 college students who lived at an altitude of 2260 m for seven months with a brief return to sea level in the middle of the period. The results were compared with 52 matched students at sea level. The conclusion was that long-term exposure to this moderate altitude had minimal effects on memory.

The effect of altitude induced hypoxia on heart disease: Do acute, intermittent, and chronic exposures provide cardioprotection?

Anderson and colleagues (p. 45) review available data on whether acute, intermittent exposure to hypoxia, and/or chronic exposure, provide protection to the myocardium in the presence of coronary artery disease. They studied current epidemiologic data as well as basic science and molecular mechanisms and, although the issue is far from settled, they concluded that many studies suggest that living at moderate altitudes provides cardiovascular protection.

Lipid profile and its association with risk factors of coronary heart disease in the high-landers of Lhasa, Tibet

Lhamo Sherpa and colleagues (p. 57) determined the prevalence of abnormal lipid levels and other risk factors for coronary heart disease in Tibetans living at an altitude of 3660 m. Cholesterol levels were measured in 371 subjects together with other risk factors such as age, sex, smoking, alcohol, physical activity, diet, and blood pressure. The important conclusion was that there is a high prevalence of hypercholesterolemia in this substantial group.

Four-year prospective study of lung function in the workers of a high altitude (4000 m) mine

Vinnikov and Redding-Jones (p. 65) studied 842 gold miners who worked at altitudes of 3800 to 4500 m over a 4-year period to try to determine whether the altitude accelerated the decline in pulmonary function. This is a difficult issue because of the confounding factors of mining, smoking, and altitude. However, the authors concluded that working at high altitude may be a factor in the deterioration of lung function in this population.

Cerebral oxygenation in awake rats during acclimation and deacclimation to hypoxia—an in vivo EPR study

In this novel study, Dunn and colleagues (p. 71) studied brain tissue PO2 in awake rats using the technique of electron paramagnetic resonance. Hypoxia was achieved by giving the animals an inspired PO2 of 10%, and this caused a decline in tissue PO2 from 26.7 to 13.0 mm Hg. Interestingly, the addition of 10% CO2 to the hypoxic gas returned the tissue PO2 values to those previously measured with the animals breathing air. Another surprising finding was that when the animals were exposed to chronic hypoxia, tissue PO2 rapidly adapted with a half time of approximately 2 days. This is a particularly interesting study using this new technique.

Adrenocortical suppression in highland chick embryos is restored during incubation at sea level

Salinas and coworkers (p. 79) tested whether development at high altitude in a chick embryo model was related to adrenocortical suppression by the hypoxia. Development of the embryos at high altitude, compared with sea level, caused adrenocortical blunting but an increase in adrenal catecholamine blood levels. There was a significant correlation between adrenocortical blunting and elevated adrenal catecholamine content, with asymmetric growth restriction, and with the degree of fetal hypoxia.

Brief Report

Oxygen saturation in healthy children aged 5 to 16 years residing in Huayllay-Peru (4340 m)

Schult and Canelo-Aybar (p. 89) measured the arterial oxygen saturation by pulse oximetry in 583 children in a rural part of Peru, altitude 4340 m. The children were aged from 5 to 16 years. The mean arterial oxygen saturation was 85.7%, and there was a positive association with age.

Letters to the Editor

Mountain rescue: the highest earthquake in Yushu

Tianyi Wu (p. 93) describes a devastating earthquake of magnitude 7.1 in Yushu County of Qinghai Province in western China in April 2010. The mean altitude of the earthquake was about 4000 m (3750 to 4878 m) and according to a news agency it caused the death of over 2000 people. Wu with a rescue team was rushed to the area but the conditions were extremely difficult because of the terrain, the cold, and the altitude. An unusual feature of the incident was that many of the rescuers developed high altitude diseases including AMS, HAPE, and HACE. This letter is a graphic account of a high altitude tragedy.

Risk assessment and emergency management of coronary heart disease at altitude

Strapazzon and colleagues (p. 97) write in response to the Clinician's Corner piece by Dehnert and Bärtsch on the risks of altitude exposure for patients with coronary artery disease.

Response by Christoph Dehnert and Peter Bärtsch to the letter by Strapazzon and colleagues

Dehnert and Bärtsch respond (p. 99).