Background: Thousand of tourists trek in the Himalayas every season and risk acute mountain sickness (AMS). Prior studies have shown that the rate of ascent is one of the primary risk factors for the development of AMS but the role of body hydration, age, gender, alcohol and medication usage, body weight, and altitude of residence continues to be in question. This study estimates the incidence of AMS at 4234 m at Pheriche in the Everest region, explores a number of risk factors predisposing trekkers to a diagnosis of AMS and attempts to quantify the relationship between the Lake Louise AMS diagnostic criteria and oxygen saturation.
Methods: Demographic data and information about risk factors felt to place trekkers at increased risk of AMS was collected from 550 trekkers for 1 mo in the fall of 1996 at 4234 m in the Everest region.
Results: Diagnosis of AMS was made in 29.8% (159 trekkers) of the study population. Low water intake (odds ratio 1.57; 95% confidence interval,1.02-2.40), the presence of respiratory symptoms (odds ratio 2.21; 95% confidence interval, 1.43-3.40), and an oxygen saturation below 85% at 4243 m (odds ratio 2.35; 95% confidence interval, 1.55-3.56) were identified as independent risk factors for AMS diagnosis in this sample. In addition, AMS risk decreased 18.7% (95% confidence interval, 3.8-31.2%) for each additional night spent between Lukla (2804 m) and the study site at 4243 m.
Conclusion: Increased reported fluid intake decreased the risk of AMS in this cross sectional prospective study. Further studies need to be done to confirm this finding before recommendations can be made. In addition the rise in the risk of AMS as the rate of ascent increased along this popular Everest trek was quantified for the first time. Finally, AMS was also associated with respiratory symptoms and with a lower oxygen saturation.