Analysis of High-Altitude De-Acclimatization Syndrome After Exposure to High Altitudes: A Cluster-Randomized Controlled Trial
This randomized cluster-controlled trial investigated high altitude deacclimatization syndrome in 2 groups returning from approximately 6 months of seasonal factory work in Lhasa, China, at an altitude of 3650 m. High altitude deacclimatization syndrome comprises a constellation of symptoms including fatigue, sleepiness, insomnia, memory loss, headache, throat pain, cough, chest tightness, appetite changes, diarrhea, abdominal pain, and arthralgias. The investigators developed a scoring system to evaluate subjects on the 3rd, 50th, and 100th day after descending from high altitude and correlated these scores with laboratory blood tests. Subjects were enrolled from Chongqing, China (n = 67, 180 m) and Kunming, China (n = 70, 1800 m), and matched with healthy control subjects who did not travel to altitude.
In both groups symptom scores peaked on day 3 after returning from high altitude, corresponding to a mild deacclimatization reaction. The most common symptoms of fatigue, dizziness, and coughing were reported in 50 to 73% of all subjects. Hematologic parameters showed expected patterns, with the hematocrit peaking while at altitude (mean, 57.9%), and returning to baseline by the 100th day after descent (mean, 43.9%). In contrast, white blood cell count, creatine kinase, creatine kinase-MB, and lactate dehydrogenase values peaked on day 3 of return and were higher than high altitude baselines. The authors suggest this finding may be attributable to hypoxia, reoxygenation-induced tissue damage, and the release of inflammatory mediators. The authors proposed their scoring system provided a framework for recognizing high altitude deacclimatization syndrome. Further research is necessary to examine deacclimatization pathophysiology and potential prevention or treatment options. Limitations of the study include a relatively small and underrepresented sample size and the lack of prior studies defining deacclimatization syndrome.
(PLoS One. 2013;8:e62072) B He, J Wang, G Qian, et al.