title: Changes in cerebral vascular reactivity and structure following prolonged exposure to high altitude in humans.
abstract: Although high-altitude exposure can lead to neurocognitive impairment, even upon return to sea level, it remains unclear the extent to which brain volume and regional cerebral vascular reactivity (CVR) are altered following high-altitude exposure. The purpose of this study was to simultaneously determine the effect of 3 weeks at 5050 m on: (1) structural brain alterations; and (2) regional CVR after returning to sea level for 1 week. Healthy human volunteers (n = 6) underwent baseline and follow-up structural and functional magnetic resonance imaging (MRI) at rest and during a CVR protocol (end-tidal PCO2 reduced by -10, -5 and increased by +5, +10, and +15 mmHg from baseline). CVR maps (% mmHg(-1)) were generated using BOLD MRI and brain volumes were estimated. Following return to sea level, whole-brain volume and gray matter volume was reduced by 0.4 ± 0.3% (P < 0.01) and 2.6 ± 1.0% (P < 0.001), respectively; white matter was unchanged. Global gray matter CVR and white matter CVR were unchanged following return to sea level, but CVR was selectively increased (P < 0.05) in the brainstem (+30 ± 12%), hippocampus (+12 ± 3%), and thalamus (+10 ± 3%). These changes were the result of improvement and/or reversal of negative CVR to positive CVR in these regions. Three weeks of high-altitude exposure is reflected in loss of gray matter volume and improvements in negative CVR.
authors.affiliation: Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada School of Kinesiology, University of British Columbia, Vancouver, Canada glen.foster@ubc.ca.
authors.forename: Glen E
authors.initials: GE
authors.lastname: Foster
authors.affiliation: Department of Ophthalmology and Visual Sciences, Faculty of Medicine, University of British Columbia, Vancouver, Canada.
authors.forename: Jodie
authors.initials: J
authors.lastname: Davies-Thompson
authors.affiliation: School of Kinesiology, University of British Columbia, Vancouver, Canada.
authors.forename: Paolo B
authors.initials: PB
authors.lastname: Dominelli
authors.affiliation: Diagnostic and Therapeutic Neuroradiology, Vancouver General Hospital University of British Columbia, Vancouver, Canada.
authors.forename: Manraj K S
authors.initials: MK
authors.lastname: Heran
authors.affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK.
authors.forename: Joseph
authors.initials: J
authors.lastname: Donnelly
authors.affiliation: Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada.
authors.forename: Gregory R
authors.initials: GR
authors.lastname: duManoir
authors.affiliation: Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada.
authors.forename: Philip N
authors.initials: PN
authors.lastname: Ainslie
authors.affiliation: Department of Radiology, UBC MRI Research Centre University of British Columbia, Vancouver, Canada.
authors.forename: Alexander
authors.initials: A
authors.lastname: Rauscher
authors.affiliation: School of Kinesiology, University of British Columbia, Vancouver, Canada.
authors.forename: A William
authors.initials: AW
authors.lastname: Sheel
keywords: Cerebral atrophy; cerebral vascular reactivity; high altitude