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.