Objectives: Clearance of the pharynx by deglutition is important in protecting the airway. The pattern of deglutition during sleep was investigated.
Methods: Deglutition during sleep was examined in 8 normal human adults via time-matched recordings of polysomnography and surface electromyography (EMG) of the thyrohyoid and suprahyoid muscles.
Results: During sleep, deglutition was episodic, and was absent for long periods. The mean number of swallows per hour (+/-SD) during the total sleep time was 2.9 +/- 1.3. The mean period of the longest absence of deglutition was 50.6 +/- 10.2 minutes. Most deglutition occurred in association with spontaneous electroencephalographic arousal in rapid eye movement (REM) sleep and non-REM sleep. Deglutition was related to sleep stage. The mean number of swallows per hour was 7.2 +/- 3.5 during stage 1 sleep and 2.0 +/- 0.7 during stage 2 sleep. There was little deglutition during stages 3 and 4. The deeper the sleep stage became, the lower the mean deglutition frequency became. The mean number of swallows per hour was 2.7 +/- 2.2 during REM sleep. The EMG amplitude dropped to the lowest level of recording and hypotonic EMG activity increased during REM sleep.
Conclusions: Deglutition, a vital function, is infrequent during sleep.