Obesity may increase mountain sickness

Obese people have been found to be at an increased risk for developing acute mountain sickness (AMS). Although the reason for this association is unclear, it appeared to be partly related to greater night-time decline in oxygen saturation levels in obese individuals.The prevalence and severity of AMS depends on several factors, such as age, gender, speed of ascent, and altitude. Findings from previous studies have suggested that obesity may be a risk factor for AMS, but this association has not been studied under controlled conditions.Researchers from the Presbyterian Hospital of Dallas, USA, measured AMS scores and oxygen saturation levels in 9 obese and 10 non-obese men who were placed in a decompression chamber that simulated a rapid climb to 12,000 feet. All of the subjects resided at sea level.The obese subjects experienced a significantly greater rise in AMS scores with altitude than did non-obese subjects. After 24 hours in the chamber, seven obese subjects and four non-obese subjects had scores of 4 or higher, the threshold for the formal diagnosis of AMS. Headache, which was reported in 89% of subjects, was the most common AMS symptom, followed by difficulty sleeping, gastrointestinal upset, and fatigue and weakness. Oxygen saturation levels were significantly lower in obese subjects than in their non-obese peers, with the lowest values observed at night.It was concluded that obesity is an important, previously unrecognised factor in the development of AMS.