High altitude sleep disturbances monitored by actigraphy and polysomnography.
AIMS
Data on sleep at altitude are scant due to the limited availability of polysomnography. Therefore, we investigated whether actigraphy might serve as a simple tool for monitoring sleep during altitude field studies.


METHODS
Fourteen mountaineers participating in studies on dexamethasone prophylaxis of high altitude pulmonary edema were monitored by actigraphy and polysomnography during 1 night at Zurich (490 m) and 4 nights at the Regina Margherita hut (4559 m). Total sleep time (TST) estimated by actigraphy was compared to polysomnography and subjective sleep quality.


RESULTS
In 64 comparisons, mean differences±2SD (bias±limits of agreement) between actigraphy and polysomnography were 5±35 min for TST and 1±7% for sleep efficiency. Correlations between subjective and polysomnographic estimates of sleep efficiency and sleep latency were nonsignificant. Medians of nocturnal oxygen saturation were 96% at 490 m and 74%-81% during nights 1 to 4 at 4459 m (p<0.05 vs. 490 m). Medians of polysomnographic TST were similar at 490 m (451 min) and 4559 m (377-456 min during nights 1 to 4, p=NS) but the proportions of slow wave and REM sleep were reduced and arousals were more common (p<0.05 all instances).


CONCLUSION
Actigraphy accurately estimates sleep efficiency and duration. Due to its portability and simple use and the potential application over several weeks, it is a convenient tool for investigating altitude effects on sleep during field studies.