Nocturnal hypoxia exposure with simulated altitude for 14 days does not significantly alter working memory or vigilance in humans.
OBJECTIVE
To assess the effect of 2 weeks of nocturnal hypoxia exposure using simulated altitude on attention and working memory in healthy adult humans.


METHODS
Prospective experimental physiological assessment.


METHODS
General Clinical Research Center.


METHODS
Eleven healthy, nonsmoking, subjects (7 men, 4 women). The subjects had a mean age of 27 +/- 1.5 years and body mass index of 23 +/- 0.9 kg/m2.


METHODS
Subjects were exposed to 9 hours of continuous hypoxia from 2200 to 0700 hours in an altitude tent. Acclimatization was accomplished by graded increases in "altitude" over 3 nights (7700, 10,000 and 13,000 feet), followed by 13,000 feet for 13 consecutive days (FIO2 0.13).


RESULTS
Polysomnography that included airflow measurements with a nasal cannula were done at baseline and during 3 time points across the protocol (nights 3, 7, and 14). Attention (10-minute Psychomotor Vigilance Task) and working memory (10-minute verbal 2-back) were assessed at baseline and on day 4, 8, 9, and 15. Nocturnal hypoxia was documented using endpoints of minimum oxygen saturation, oxygen desaturation index, and percentage of total sleep time under 90% and 80%. Total sleep time was reduced, stage 1 sleep was increased, and both obstructive and nonobstructive respiratory events were induced by altitude exposure. There was no difference in subjective mood, attention, or working memory.


CONCLUSIONS
Two weeks of nocturnal continuous hypoxia in an altitude tent did not induce subjective sleepiness or impair objective vigilance and working memory. Caution is recommended in the extrapolation to humans the effects of hypoxia in animal models.
Thomas
Robert Joseph
RJ
Beth Israel Deaconess Medical School & Harvard Medical School, Boston, MA 02215, USA. rthomas1@bidmc.harvard.edu
Tamisier
Renaud
R
Boucher
Judith
J
Kotlar
Yana
Y
Vigneault
Kevin
K
Weiss
J Woodrow
JW
Gilmartin
Geoffrey
G
D000064:Acclimatization; D000328:Adult; D001143:Arousal / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D020920:Dyssomnias / Q000209:etiology; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000150:complications*; D008297:Male; D008568:Memory / Q000502:physiology*; D008569:Memory Disorders / Q000209:etiology; D017286:Polysomnography; D012892:Sleep Deprivation / Q000150:complications; D012894:Sleep Stages / Q000502:physiology