Ambient Temperature and Obstructive Sleep Apnea: Effects on Sleep, Sleep Apnea, and Morning Alertness

Study Objectives: The aim of the study was to investigate the effect of ambient temperature on sleep, sleep apnea, and morning alertness in patients with obstructive sleep apnea. Design: Randomized controlled trial. Setting: In-hospital investigations. Participants: Forty patients with obstructive sleep apnea naive to treatment, with an apnea-hypopnea index of 10-30. Interventions: Three different nights in room temperatures of 16 degrees C, 20 degrees C, and 24 degrees C. Measurements: Overnight polysomnography and Karolinska Sleepiness Scale. Results: The obstructive apnea-hypopnea index was 30 +/- 17 at 16 degrees C room temperature, 28 +/- 17 at 20 degrees C, and 24 +/- 18 at 24 degrees C. The obstructive apnea-hypopnea index was higher at 16 degrees C room temperature versus 24 degrees C (P = 0.001) and at 20 degrees C room temperature versus 24 degrees C (P = 0.033). Total sleep time was a mean of 30 min longer (P = 0.009), mean sleep efficiency was higher (77 +/- 11% versus 71 +/- 13% respectively, P = 0.012), and the patients were significantly more alert according to the Karolinska Sleepiness Scale (P < 0.028) in the morning at 16 degrees C room temperature versus 24 degrees C. The amount of sleep in different sleep stages was not affected by room temperature. Conclusions: Untreated patients with obstructive sleep apnea sleep longer, have better sleep efficiency, and are more alert in the morning after a night's sleep at 16 degrees C room temperature compared with 24 degrees C, but obstructive sleep apnea is more severe at 16 degrees C and 20 degrees C compared with 24 degrees C.