Caudwell xtreme everest: A prospective study of the effects of environmental hypoxia on cognitive functioning

Caudwell Xtreme Everest Research Group

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Background: The neuropsychological consequences of exposure to environmental hypobaric hypoxia (EHH) remain unclear. We thus investigated them in a large group of healthy volunteers who trekked to Mount Everest base camp (5,300 m). Methods: A neuropsychological (NP) test battery assessing memory, language, attention, and executive function was administered to 198 participants (age 44.5±13.7 years; 60% male). These were studied at baseline (sea level), 3,500 m (Namche Bazaar), 5,300 m (Everest Base Camp) and on return to 1,300 m (Kathmandu) (attrition rate 23.7%). A comparable control group (n = 25; age 44.5±14.1 years; 60% male) for comparison with trekkers was tested at/or near sea level over an equivalent timeframe so as to account for learning effects associated with repeat testing. The Reliable Change Index (RCI) was used to calculate changes in cognition and neuropsychological function during and after exposure to EHH relative to controls. Results: Overall, attention, verbal ability and executive function declined in those exposed to EHH when the performance of the control group was taken into account (RCI .05 to -.95) with decline persisting at descent. Memory and psychomotor function showed decline at highest ascent only (RCI -.08 to -.56). However, there was inter-individual variability in response: whilst NP performance declined in most, this improved in some trekkers. Cognitive decline was greater amongst older people (r = .42; p < .0001), but was otherwise not consistently associated with socio-demographic, mood, or physiological variables. Conclusions: After correcting for learning effects, attention, verbal abilities and executive functioning declined with exposure to EHH. There was considerable individual variability in the response of brain function to sustained hypoxia with some participants not showing any effects of hypoxia. This might have implications for those facing sustained hypoxia as a result of any disease.

Original languageEnglish (US)
Article numbere0174277
JournalPLoS One
Volume12
Issue number3
DOIs
StatePublished - Mar 1 2017

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prospective studies
hypoxia
Prospective Studies
Environmental Exposure
Sea level
Aptitude
Executive Function
Oceans and Seas
Data storage equipment
sea level
learning
Learning
Control Groups
Brain
Neuropsychological Tests
emotions
Hypoxia
cognition
Cognition
volunteers

ASJC Scopus subject areas

  • Medicine(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)

Cite this

Caudwell xtreme everest : A prospective study of the effects of environmental hypoxia on cognitive functioning. / Caudwell Xtreme Everest Research Group.

In: PLoS One, Vol. 12, No. 3, e0174277, 01.03.2017.

Research output: Contribution to journalArticle

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abstract = "Background: The neuropsychological consequences of exposure to environmental hypobaric hypoxia (EHH) remain unclear. We thus investigated them in a large group of healthy volunteers who trekked to Mount Everest base camp (5,300 m). Methods: A neuropsychological (NP) test battery assessing memory, language, attention, and executive function was administered to 198 participants (age 44.5±13.7 years; 60{\%} male). These were studied at baseline (sea level), 3,500 m (Namche Bazaar), 5,300 m (Everest Base Camp) and on return to 1,300 m (Kathmandu) (attrition rate 23.7{\%}). A comparable control group (n = 25; age 44.5±14.1 years; 60{\%} male) for comparison with trekkers was tested at/or near sea level over an equivalent timeframe so as to account for learning effects associated with repeat testing. The Reliable Change Index (RCI) was used to calculate changes in cognition and neuropsychological function during and after exposure to EHH relative to controls. Results: Overall, attention, verbal ability and executive function declined in those exposed to EHH when the performance of the control group was taken into account (RCI .05 to -.95) with decline persisting at descent. Memory and psychomotor function showed decline at highest ascent only (RCI -.08 to -.56). However, there was inter-individual variability in response: whilst NP performance declined in most, this improved in some trekkers. Cognitive decline was greater amongst older people (r = .42; p < .0001), but was otherwise not consistently associated with socio-demographic, mood, or physiological variables. Conclusions: After correcting for learning effects, attention, verbal abilities and executive functioning declined with exposure to EHH. There was considerable individual variability in the response of brain function to sustained hypoxia with some participants not showing any effects of hypoxia. This might have implications for those facing sustained hypoxia as a result of any disease.",
author = "{Caudwell Xtreme Everest Research Group} and Konstadina Griva and Jan Stygall and Wilson, {Mark H.} and Daniel Martin and Denny Levett and Kay Mitchell and Monty Mythen and Montgomery, {Hugh E.} and Grocott, {Mike P.} and Golnar Aref-Adib and Mark Edsell and Tracie Plant and Chris Imray and Debbie Cooke and Jane Harrington and Maryam Khosravi and Newman, {Stanton P.} and V. Ahuja and R. Burnham and A. Chisholm and K. Clarke and D. Coates and M. Coates and D. Cook and M. Cox and S. Dhillon and C. Dougall and P. Doyle and P. Duncan and L. Edwards and L. Evans and P. Gardiner and P. Gunning and N. Hart and J. Harvey and C. Holloway and D. Howard and D. Hurlbut and C. Ince and M. Jonas and {Van Der Kaaij}, J. and N. Kolfschoten and H. Luery and A. Luks and R. McMorrow and P. Meale and G. Morgan and J. Morgan and A. Murray and Rodway, {George W}",
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T2 - A prospective study of the effects of environmental hypoxia on cognitive functioning

AU - Caudwell Xtreme Everest Research Group

AU - Griva, Konstadina

AU - Stygall, Jan

AU - Wilson, Mark H.

AU - Martin, Daniel

AU - Levett, Denny

AU - Mitchell, Kay

AU - Mythen, Monty

AU - Montgomery, Hugh E.

AU - Grocott, Mike P.

AU - Aref-Adib, Golnar

AU - Edsell, Mark

AU - Plant, Tracie

AU - Imray, Chris

AU - Cooke, Debbie

AU - Harrington, Jane

AU - Khosravi, Maryam

AU - Newman, Stanton P.

AU - Ahuja, V.

AU - Burnham, R.

AU - Chisholm, A.

AU - Clarke, K.

AU - Coates, D.

AU - Coates, M.

AU - Cook, D.

AU - Cox, M.

AU - Dhillon, S.

AU - Dougall, C.

AU - Doyle, P.

AU - Duncan, P.

AU - Edwards, L.

AU - Evans, L.

AU - Gardiner, P.

AU - Gunning, P.

AU - Hart, N.

AU - Harvey, J.

AU - Holloway, C.

AU - Howard, D.

AU - Hurlbut, D.

AU - Ince, C.

AU - Jonas, M.

AU - Van Der Kaaij, J.

AU - Kolfschoten, N.

AU - Luery, H.

AU - Luks, A.

AU - McMorrow, R.

AU - Meale, P.

AU - Morgan, G.

AU - Morgan, J.

AU - Murray, A.

AU - Rodway, George W

PY - 2017/3/1

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N2 - Background: The neuropsychological consequences of exposure to environmental hypobaric hypoxia (EHH) remain unclear. We thus investigated them in a large group of healthy volunteers who trekked to Mount Everest base camp (5,300 m). Methods: A neuropsychological (NP) test battery assessing memory, language, attention, and executive function was administered to 198 participants (age 44.5±13.7 years; 60% male). These were studied at baseline (sea level), 3,500 m (Namche Bazaar), 5,300 m (Everest Base Camp) and on return to 1,300 m (Kathmandu) (attrition rate 23.7%). A comparable control group (n = 25; age 44.5±14.1 years; 60% male) for comparison with trekkers was tested at/or near sea level over an equivalent timeframe so as to account for learning effects associated with repeat testing. The Reliable Change Index (RCI) was used to calculate changes in cognition and neuropsychological function during and after exposure to EHH relative to controls. Results: Overall, attention, verbal ability and executive function declined in those exposed to EHH when the performance of the control group was taken into account (RCI .05 to -.95) with decline persisting at descent. Memory and psychomotor function showed decline at highest ascent only (RCI -.08 to -.56). However, there was inter-individual variability in response: whilst NP performance declined in most, this improved in some trekkers. Cognitive decline was greater amongst older people (r = .42; p < .0001), but was otherwise not consistently associated with socio-demographic, mood, or physiological variables. Conclusions: After correcting for learning effects, attention, verbal abilities and executive functioning declined with exposure to EHH. There was considerable individual variability in the response of brain function to sustained hypoxia with some participants not showing any effects of hypoxia. This might have implications for those facing sustained hypoxia as a result of any disease.

AB - Background: The neuropsychological consequences of exposure to environmental hypobaric hypoxia (EHH) remain unclear. We thus investigated them in a large group of healthy volunteers who trekked to Mount Everest base camp (5,300 m). Methods: A neuropsychological (NP) test battery assessing memory, language, attention, and executive function was administered to 198 participants (age 44.5±13.7 years; 60% male). These were studied at baseline (sea level), 3,500 m (Namche Bazaar), 5,300 m (Everest Base Camp) and on return to 1,300 m (Kathmandu) (attrition rate 23.7%). A comparable control group (n = 25; age 44.5±14.1 years; 60% male) for comparison with trekkers was tested at/or near sea level over an equivalent timeframe so as to account for learning effects associated with repeat testing. The Reliable Change Index (RCI) was used to calculate changes in cognition and neuropsychological function during and after exposure to EHH relative to controls. Results: Overall, attention, verbal ability and executive function declined in those exposed to EHH when the performance of the control group was taken into account (RCI .05 to -.95) with decline persisting at descent. Memory and psychomotor function showed decline at highest ascent only (RCI -.08 to -.56). However, there was inter-individual variability in response: whilst NP performance declined in most, this improved in some trekkers. Cognitive decline was greater amongst older people (r = .42; p < .0001), but was otherwise not consistently associated with socio-demographic, mood, or physiological variables. Conclusions: After correcting for learning effects, attention, verbal abilities and executive functioning declined with exposure to EHH. There was considerable individual variability in the response of brain function to sustained hypoxia with some participants not showing any effects of hypoxia. This might have implications for those facing sustained hypoxia as a result of any disease.

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