An Epidemiological Investigation Of Acute Mountain Sickness In Tourist Population In Lake NaMuCuo

Objectives: Low concentration and pressure of oxygen in the atmosphere of high altitude area can lead to many altitude related illnesses in the population those ascending quickly from low land to altitude in a short time. Acute mountain sickness (AMS) which is caused by hypobaric hypoxia may pose a threaten to the health of tourists. Acute mountain response (which is uauslly called AMS), high altitude cerebral edema (HACE) and high altitude pulmonary edema (HAPE) are the three common froms of AMS. From this sampling survey, we want to find out: (1) the incidence and distribution of Acute mountain sickness in the population of tourists. (2) the risk fators of Acute mountain sickness in the tourist population.Methods: five local tourism agencies in Lhasa were selected by cluster sampling in the hot tourism reason from sept. 5. 2008 to sept. 10. 2008. We cooperated with these tourism agencies to investigate a subgroup of tourist population in NaMuCuo in the Tibetan Plateau. Subjects enrolled in by following criteria:(1)older than or equal to 15 years old and those participated the investigation voluntarily and came from domestic population; (2) the first travel location is NaMuCuo after reaching at Lhasa. According to the Lake Louise scoring system, AMS is diagnosed by the following criterion: (1) entering into high altitude area; (2) headache; (3) At least presence of one of following symptoms: gastrointestinal symptoms; fatigue and/ or weakness and dizziness/ lightheadedness; (4) the Lake Louise score≥3. HACE and HAPE were diagnosed by the field investigation criterion approved by the division of mountain medicine of Chinese Medical Association in its third national symposium. All subjects were surveyed by the uniformed questionnaire which contains questions about health status and related exposure fators. The data was analized by SPSS 13. 0, specific AMS incidences were compared among exposure factors, incidence of AMS between two groups or multiple groups were analized by chi square test. Multiple-factor analysis was performed by logistic regression. P≤0.05 was supposed to be statistical significant.Results: After depleting 3 invalid questionnaires, We analyzed 307 valid questionnaires when it was the completion of the collection of 310 questionnaires. The response rates of 20 factors ranged from 82.41% to 99.67%. Male accounts for 55.4%(170/307), and female accounts for 44.6%(137/307). Mean age is 37.3±11.8 years old with a range from 18 to 72 years old. Reported incidence of AMS is 42.3%(130/307, 95.0%CI= 36.8%~47.8%), and reported incidence of symptom of AMS is 76.9% (236/307, 95.0%CI= 72.2%~81.6%). There was no reported case of HACE or HAPE.The incidence of AMS in male is 38. 24%, and 47.45% in female( x~2=2.636,P=0.104), the age-specific incidence of AMS in three age groups of 15~30 years old, 31~50 years old and older than 50 years old are 33.33%, 42.37%, 43.59% respectively( x~2=2.201,P=0.333). The specific incidence of AMS in the population from western, northern and southern of china are 42.86%, 41.03% and 39.05%( x~2=0.257,P=0.879). The peak time of occurrence of AMS is 0~0.5 hour and 0.5~1.0 hour after reaching at NaMuCuo, the number of AMS in the two periods account for 81.61% of the total cases. From single- factor analysis, we found that personal mood before reaching at NaMuCuo, kinds of vehicle to Lhasa, history of AMS and family history of AMS are correlated with the incidence of AMS significantly. Personal mood in 48 hours before reaching at NaMuCuo, kinds of vehicle to Lhasa are also correlated with the incidence of AMS using multiple- factor analysis method. Gender, age, education level, blood type, body mass index, health status, the first psychic reaction to the traveling to the high altitude, alcohol drinking, upper respiratory infection, high altitude experiences, knowledge of high altitude medicine and preventive measures are not correlated with the incidence of AMS.Conclusion: The incidence of AMS is relatively high in the tourist pupoltion after quick ascent from Lhasa to MaNuCuo. Personal mood during traveling, rate of ascent, history of AMS and family history of AMS are probably the risk factors of AMS in this study pupolation. So we suggest that people those who want to travel to NaMuCuo should adjust their mood and take a lower speech of vehicle when they are traveling to avoid AMS, and promoting educational programs on AMS to help those who have a history of AMS and those who have a family history of AMS to prevent AMS.