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Circadian patterns in men acclimatized to intermittent hypoxia
M Vargas1, D Jiménez, F León-Velarde
1Centro de Investigación en Medicina de Altura, Mutual de Seguridad C. Ch. C., Iquique, Chile.
Respiration Physiology
|June 14, 2001
Summary
High altitude (HA) hypoxia alters circadian rhythms in humans, affecting body temperature and blood pressure oscillations. These changes may contribute to sleep disturbances at HA and in those with cardiorespiratory issues.
Area of Science:
- Human physiology
- Circadian biology
- Altitude medicine
Background:
- Circadian rhythms regulate physiological processes.
- Hypoxia at high altitude (HA) is known to affect physiology.
- Understanding hypoxia's impact on human circadian patterns is crucial.
Purpose of the Study:
- To investigate the effects of high altitude (HA) hypoxia on circadian rhythm amplitudes in humans.
- To compare circadian oscillations at HA (3800 m) versus sea level (SL).
Main Methods:
- Six men underwent a 24-hour constant routine protocol.
- Measurements were taken during high altitude (HA) and sea level (SL) shifts.
- Circadian oscillation amplitudes of physiological variables were analyzed.
Main Results:
- Circadian amplitudes for oxygen consumption, breathing rate, thoracic skin temperature, and diastolic pressure did not differ between HA and SL.
- Tympanic temperature amplitude was lower, while calf temperature amplitude was higher at HA compared to SL.
- End-tidal P(CO2) and systolic pressure showed larger amplitude oscillations at HA.
Conclusions:
- Hypoxia at HA demonstrably affects specific human circadian patterns, including thermoregulation.
- Altered circadian rhythms under hypoxia may underlie sleep disturbances at HA.
- Findings have implications for cardiorespiratory patients experiencing hypoxia.