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Trekkers’ Awareness of Acute Mountain Sickness and Acetazolamide
Letters to the Editor
321
Trekkers’ Awareness of Acute Mountain Sickness and Acetazolamide To the Editor: Despite the wealth of information about acute mountain sickness (AMS) and the value of acetazolamide for its prevention and treatment, we have encountered many trekkers to high altitude who seem confused about the use of acetazolamide in AMS. There appears to be a misconception that acetazolamide masks early AMS symptoms; this is mentioned in some guidebooks.1 We have not found any references to the extent of acetazolamide usage by trekkers for AMS prevention. To test the level of trekkers’ understanding of AMS and the use of acetazolamide, we performed a crosssectional study. Formatted interviews were conducted in English with 150 trekkers at Mislung, the exit point from Namche Bazar (3440 m altitude) in the Solukhumbu (Everest) region of Nepal on 3 consecutive days in October 2001. Trekkers were assessed for symptoms of AMS using the Lake Louise Questionnaire scoring system; a score of 3 or more, including headache plus at least one other symptom, was the diagnostic criterion for AMS.2 Trekkers were asked whether they thought that they had had AMS, whether they had used acetazolamide, and whether they believed that acetazolamide masked AMS symptoms. On day 1, many trekkers (19 of 55) mentioned that they had visited the Himalayan Rescue Association (HRA) clinic at Pheriche (4234 m). Some had attended lectures on AMS (lectures delivered at the HRA clinic in English covering basic understanding of AMS and its management), and others had not. The question regarding attendance at lectures was not in the
Table 1. Trekker characteristics and acute mountain sickness (AMS) Lake Louise Questionnaire scores Mean age No. of males No. of females Mean Lake Louise score Total no. with AMS No. of males with AMS No. of females with AMS
38.6 years 98 52 4.83 58/150 36/98 22/52
(range 18–65) (65.3%) (34.7%) (SD 1.94) (38.7%) (36.1%) (42.3%)
original interview protocol, but these observations prompted us to include a question on attendance at lectures in the interviews on days 2 and 3. Therefore, only 95 of 150 trekkers were asked a question about attending lectures at Pheriche and/or elsewhere. The results of the study are shown in Tables 1 and 2; additional data are provided. There was no statistically significant gender difference in the frequency of reporting AMS symptoms (P ⫽ .597, Fisher exact test). Only 34 of 58 (58.6%) trekkers with a Lake Louise score of 3 or higher thought that they had suffered from AMS; most of the rest (20 of 58, 34.5%) denied having had AMS, and a few (4 of 58, 6.9%) were unsure about the cause of their symptoms. Acetazolamide was taken for AMS prevention by 27 of 150 (18.0%) trekkers and for treatment by 16 (10.7%). When asked whether acetazolamide masked AMS, 27 of 150 (18.0%) trekkers believed that it did. Of the rest, 63 (42.0%) did not believe that acetazolamide masked AMS symptoms; 60 (40.0%) were unsure whether or not acetazolamide masked AMS symptoms. Lectures on AMS had been attended by only 40 of 95 (42.1%) trekkers. Of these 40 trekkers, 11 attended lectures at Pheriche only, 19 attended them elsewhere only, and 5 attended lectures both at Pheriche and elsewhere. Our study showed trekkers’ lack of understanding of AMS and of the proven benefit of acetazolamide for its prevention3,4 and treatment.5 Attendance at lectures conferred no statistically significant benefit on trekkers’ understanding of either of these issues. However, this was a small study with insufficient numbers to draw any firm conclusions. Because this was a retrospective study, the accuracy of trekkers’ memories of their symptoms could also be questioned. The lack of details about the quality and type of lectures (except for those delivered at the HRA clinic in Pheriche) was another limitation of our study. Perhaps lectures could be improved, reinforced by concise and authoritative written information that is distributed immediately before the start of a trek. Acute mountain sickness remains common in trekkers to high altitudes because time constraints and inflexible trekking schedules result in a rapid ascent rate. It is still often unrecognized despite widely available information. More strenuous efforts are needed to reinforce the message that trekkers must recognize the symptoms and signs of AMS and realize their individual responsibilities.
322
Letters to the Editor
Table 2. Effect of lectures on the understanding of acetazolamide’s (Az) effect and on the awareness of acute mountain sickness (AMS) No. of trekkers who attended lectures Az masks AMS Az does not mask AMS Unsure whether Az masks AMS Aware of AMS Unaware of AMS Unsure what caused symptoms
7/40 16/40 17/40 10/16 4/16 2/16
(17.5%) (40.0%) (42.5%) (62.5%) (25%) (12.5%)
Deepak Subedi, MB, BS Ramesh Marahatta, MB, BS Shailendra Sharma, MB, BS Rajan Bajracharya, MB, BS Kathmandu, Nepal Peter Hillenbrand, MB West Midlands, United Kingdom Yuen Soon, MB Birmingham Medical Research Expeditionary Society Birmingham, United Kingdom References 1. Lonely Planet Health. Heat, cold, high altitude and motion sickness. Available at: http://www.lonelyplanet.com/health/ heat.htm#alt. Accessed November 6, 2006.
No. of trekkers who did not attend lectures 13/55 17/55 25/55 15/26 11/26 0
(23.6%) (30.9%) (45.5%) (57.7%) (42.3%)
Statistical significance (Fisher exact test) P ⫽ .612 P ⫽ .389 P ⫽ 1.0 P ⫽ .330
2. Roach RC, Ba¨rtsch P, Oelz O, Hackett PH, Lake Louise AMS Scoring Consensus Committee. The Lake Louise acute mountain sickness scoring system. In: Sutton JR, Houston CS, Coates G, eds. Hypoxia and Molecular Medicine. Burlington, VT: Charles S Houston, 1993:272–274. 3. Gertsch JH, Basnyat B, Johnson EW, Onopa J, Holck PS. Randomised, double blind, placebo controlled comparison of ginkgo biloba and acetazolamide for prevention of acute mountain sickness among Himalayan trekkers: the prevention of high altitude illness trial (PHAIT). BMJ. 2004;328: 797–801. 4. Basnyat B, Gertsch JH, Johnson EW, Castro-Marin F, Inoue Y, Yeh C. Efficacy of low-dose acetazolamide (125 mg BID) for the prophylaxis of acute mountain sickness: a prospective, double-blind, randomized, placebo-controlled trial. High Alt Med Biol. 2003;4:45–52. 5. Birmingham Medical Research Expeditionary Society. Mountain Sickness Study Group. Acetazolamide in control of acute mountain sickness. Lancet. 1981;ii:180–183.
321
Trekkers’ Awareness of Acute Mountain Sickness and Acetazolamide To the Editor: Despite the wealth of information about acute mountain sickness (AMS) and the value of acetazolamide for its prevention and treatment, we have encountered many trekkers to high altitude who seem confused about the use of acetazolamide in AMS. There appears to be a misconception that acetazolamide masks early AMS symptoms; this is mentioned in some guidebooks.1 We have not found any references to the extent of acetazolamide usage by trekkers for AMS prevention. To test the level of trekkers’ understanding of AMS and the use of acetazolamide, we performed a crosssectional study. Formatted interviews were conducted in English with 150 trekkers at Mislung, the exit point from Namche Bazar (3440 m altitude) in the Solukhumbu (Everest) region of Nepal on 3 consecutive days in October 2001. Trekkers were assessed for symptoms of AMS using the Lake Louise Questionnaire scoring system; a score of 3 or more, including headache plus at least one other symptom, was the diagnostic criterion for AMS.2 Trekkers were asked whether they thought that they had had AMS, whether they had used acetazolamide, and whether they believed that acetazolamide masked AMS symptoms. On day 1, many trekkers (19 of 55) mentioned that they had visited the Himalayan Rescue Association (HRA) clinic at Pheriche (4234 m). Some had attended lectures on AMS (lectures delivered at the HRA clinic in English covering basic understanding of AMS and its management), and others had not. The question regarding attendance at lectures was not in the
Table 1. Trekker characteristics and acute mountain sickness (AMS) Lake Louise Questionnaire scores Mean age No. of males No. of females Mean Lake Louise score Total no. with AMS No. of males with AMS No. of females with AMS
38.6 years 98 52 4.83 58/150 36/98 22/52
(range 18–65) (65.3%) (34.7%) (SD 1.94) (38.7%) (36.1%) (42.3%)
original interview protocol, but these observations prompted us to include a question on attendance at lectures in the interviews on days 2 and 3. Therefore, only 95 of 150 trekkers were asked a question about attending lectures at Pheriche and/or elsewhere. The results of the study are shown in Tables 1 and 2; additional data are provided. There was no statistically significant gender difference in the frequency of reporting AMS symptoms (P ⫽ .597, Fisher exact test). Only 34 of 58 (58.6%) trekkers with a Lake Louise score of 3 or higher thought that they had suffered from AMS; most of the rest (20 of 58, 34.5%) denied having had AMS, and a few (4 of 58, 6.9%) were unsure about the cause of their symptoms. Acetazolamide was taken for AMS prevention by 27 of 150 (18.0%) trekkers and for treatment by 16 (10.7%). When asked whether acetazolamide masked AMS, 27 of 150 (18.0%) trekkers believed that it did. Of the rest, 63 (42.0%) did not believe that acetazolamide masked AMS symptoms; 60 (40.0%) were unsure whether or not acetazolamide masked AMS symptoms. Lectures on AMS had been attended by only 40 of 95 (42.1%) trekkers. Of these 40 trekkers, 11 attended lectures at Pheriche only, 19 attended them elsewhere only, and 5 attended lectures both at Pheriche and elsewhere. Our study showed trekkers’ lack of understanding of AMS and of the proven benefit of acetazolamide for its prevention3,4 and treatment.5 Attendance at lectures conferred no statistically significant benefit on trekkers’ understanding of either of these issues. However, this was a small study with insufficient numbers to draw any firm conclusions. Because this was a retrospective study, the accuracy of trekkers’ memories of their symptoms could also be questioned. The lack of details about the quality and type of lectures (except for those delivered at the HRA clinic in Pheriche) was another limitation of our study. Perhaps lectures could be improved, reinforced by concise and authoritative written information that is distributed immediately before the start of a trek. Acute mountain sickness remains common in trekkers to high altitudes because time constraints and inflexible trekking schedules result in a rapid ascent rate. It is still often unrecognized despite widely available information. More strenuous efforts are needed to reinforce the message that trekkers must recognize the symptoms and signs of AMS and realize their individual responsibilities.
322
Letters to the Editor
Table 2. Effect of lectures on the understanding of acetazolamide’s (Az) effect and on the awareness of acute mountain sickness (AMS) No. of trekkers who attended lectures Az masks AMS Az does not mask AMS Unsure whether Az masks AMS Aware of AMS Unaware of AMS Unsure what caused symptoms
7/40 16/40 17/40 10/16 4/16 2/16
(17.5%) (40.0%) (42.5%) (62.5%) (25%) (12.5%)
Deepak Subedi, MB, BS Ramesh Marahatta, MB, BS Shailendra Sharma, MB, BS Rajan Bajracharya, MB, BS Kathmandu, Nepal Peter Hillenbrand, MB West Midlands, United Kingdom Yuen Soon, MB Birmingham Medical Research Expeditionary Society Birmingham, United Kingdom References 1. Lonely Planet Health. Heat, cold, high altitude and motion sickness. Available at: http://www.lonelyplanet.com/health/ heat.htm#alt. Accessed November 6, 2006.
No. of trekkers who did not attend lectures 13/55 17/55 25/55 15/26 11/26 0
(23.6%) (30.9%) (45.5%) (57.7%) (42.3%)
Statistical significance (Fisher exact test) P ⫽ .612 P ⫽ .389 P ⫽ 1.0 P ⫽ .330
2. Roach RC, Ba¨rtsch P, Oelz O, Hackett PH, Lake Louise AMS Scoring Consensus Committee. The Lake Louise acute mountain sickness scoring system. In: Sutton JR, Houston CS, Coates G, eds. Hypoxia and Molecular Medicine. Burlington, VT: Charles S Houston, 1993:272–274. 3. Gertsch JH, Basnyat B, Johnson EW, Onopa J, Holck PS. Randomised, double blind, placebo controlled comparison of ginkgo biloba and acetazolamide for prevention of acute mountain sickness among Himalayan trekkers: the prevention of high altitude illness trial (PHAIT). BMJ. 2004;328: 797–801. 4. Basnyat B, Gertsch JH, Johnson EW, Castro-Marin F, Inoue Y, Yeh C. Efficacy of low-dose acetazolamide (125 mg BID) for the prophylaxis of acute mountain sickness: a prospective, double-blind, randomized, placebo-controlled trial. High Alt Med Biol. 2003;4:45–52. 5. Birmingham Medical Research Expeditionary Society. Mountain Sickness Study Group. Acetazolamide in control of acute mountain sickness. Lancet. 1981;ii:180–183.