Submitted on March 20, 2007
Accepted on August 7, 2007
Changes in Sleep Quality of Athletes under Normobaric Hypoxia Equivalent to 2,000m Altitude: a Polysomnographic Study
Masako Hoshikawa1*, Sunao Uchida2, Takayuki Sugo1, Yasuko Kumai3, Yoshiteru Hanai1, and Takashi Kawahara3
1 Department of Sports Science, Japan Institute of Sports Sciences, Tokyo, Japan
2 Faculty of Sport Sciences, Waseda University, Tokyo, Japan
3 Department of Sports Medicine, Japan Institute of Sports Sciences, Tokyo, Japan
* To whom correspondence should be addressed. E-mail: hoshikawa_masako{at}yahoo.co.jp.
This study evaluated the sleep quality of athletes in normobaric hypoxia at a simulated altitude of 2,000m. Eight male athletes slept in normoxic condition (NC) and hypoxic conditions equivalent to those at 2,000m altitude (HC). Polysomnographic recordings of sleep included the electroencephalogram (EEG), electrooculogram, chin surface electromyogram, and electrocardiogram. Thoracic and abdominal motion, nasal / oral airflow and blood oxygen saturation (SaO2) were also recorded. Standard visual sleep stage scoring and fast Fourier transformation analyses of the EEG were performed on 30-sec epochs. Subjective sleepiness and urinary catecholamines were also monitored. Mean SaO2 decreased and respiratory disturbances increased with HC. The increase in respiratory disturbances was significant, but the increase was small and sub clinical. The duration of slow-wave sleep (stages 3+4) and total delta power (< 3Hz) of the all-night NREM sleep EEG decreased for HC compared to NC. Subjective sleepiness and amounts of urinary catecholamines did not differ between the conditions. These results indicate that acute exposure to normobaric hypoxia equivalent to that at 2,000 m altitude decreased slow-wave sleep in athletes, but did not change subjective sleepiness or amounts of urinary catecholamines.
