Who Should Not Go High: Chronic Disease and Work at Altitude During Construction of the Qinghai-Tibet Railroad

Abstract

From 2001 to 2005, a new railroad linking Beijing with Lhasa was built by more than 100,000 workers, of whom 80% traveled from their lowland habitat to altitudes up to 5000 m to work on the railroad. We report on the medical conditions of 14,050 of these altitude workers, specifically with regard to preexisting illness. All subjects were seen at low and high altitude. Average age was 29.5 +/- 7.4 (SD) yr, range 20 to 62 yr; 98.8% of the subjects were men and 1.2% were women. Overall incidence of AMS upon first-time exposure was 51%, that of HACE 0.28%, and that of HAPE 0.49%. About 1% of the subjects were hypertensive before altitude exposure. Those with blood pressure >or=160/95 were excluded from employment at altitude. Altitude exposure led to a greater increase of blood pressure in hypertensives compared to normotensives. On prealtitude screening prevalence of cardiac arrhythmias was 0.33%. Since the majority of these were rather benign and occurring in young and otherwise healthy subjects, we allowed altitude employment. Follow-up at altitude was uneventful. Subjects with coronary heart disease and diabetes were excluded from altitude employment. Obesity was a risk factor for acute mountain sickness and for reduced work performance at altitude. Overweight subjects lost more weight during their altitude stay than subjects with normal weight. Altitude exposure was a risk factor for upper gastrointestinal tract bleeding, especially in combination with alcohol, aspirin, and dexamethasone intake. Asthmatic subjects generally did better at altitude compared to low altitude, with the exception of one subject who experienced an asthma episode from pollen exposure. In conclusion, careful evaluation of preexisting chronic illness and risk factors allowed prevention of altitude deterioration of a preexisting health condition, all the while allowing subjects with some specific conditions to work and live at altitude without problems.

Obesity as a Conditioning Factor for High-Altitude Diseases

“…Additionally, during longer CIH shifts (months) at altitudes between 4,630 and 4,905 m, subjects with a BMI > 28 kg/m 2 had a higher PAP (∼31 mm Hg) than those with a BMI of 22-24 kg/m 2 (∼22 mm Hg). Moreover, obese subjects were three times more susceptible to AMS than those with a normal BMI (97% vs. 37%) [55]. Further support comes from Yang et al [35], who demonstrated a positive correlation of a high BMI with the incidence of AMS at 3,658 m.…”

“…Regarding HAPH, it has been reported that native subjects at altitudes between 4,630 and 4,905 m with a high BMI have a higher PAP (∼31 mm Hg) than those with a normal BMI [55]. …”

Inactivation of Corticotropin-Releasing Hormone–Induced Insulinotropic Role by High-Altitude Hypoxia

“…High-altitude hypoxia often induces dysfunction and illness, particularly acute mountain sickness (AMS) (1). During the construction of the QinghaiTibet railway (at altitudes of 3,000-5,000 m) in China, .100,000 construction workers were involved, and 51% of them developed AMS (2). Moreover, since the railway began service, .10 million travelers have visited the Tibet region in 2012, of whom 31% developed AMS despite traveling with an oxygen supply on the train (3).…”

High-altitude headache and acute mountain sickness

“…HACE is a potentially highly severe encephalopathy that may affect 0.5% to 1% of all individuals suffering from AMS. 31 In addition, it is estimated that 5% of non-acclimated individuals may present cerebral oedema above 4500 m. The incidence of high-altitude pulmonary oedema is approximately 2%. 32…”