[Aspects of sleep effects on the digestive tract]

During sleep the gastrointestinal system function is markedly reduced most of the time.

In this revision we described the effect of sleep on the digestive system. Salivation, swallowing rate, upper esophageal sphincter pressure and number of primary esophageal contractions have all been shown to be reduced during sleep.

Gastric emptying is slow during sleep but the REM sleep is associated with faster gastric emptying. During the night we have a more regular intestinal motility than during the day. During sleep, phase II of the migrating motor complex cycle is virtually absent, both during diurnal or nocturnal sleep. The nocturnal velocity of migrating motor complex propagation in the proximal small bowel is slower than the diurnal velocity. The colon has a decrease in tonus and contractions. The anal canal pressure is lower and rectum activity is higher during sleep than during the awake state, but the anal pressure is still higher than the rectum pressure and the rectum contractions are most frequently retrograde.

Transient lower esophageal sphincter relaxation is the most frequent cause of gastroesophageal reflux. The frequency of this transient relaxation is very low during sleep. Gastroesophageal reflux during sleep is more frequently associated with a low lower esophageal sphincter pressure.

In this situation the disease is worse because the patient is in the supine position, so gravity does not help the acid esophageal clearance, salivation is decreased and the primary esophageal contraction is not frequent, a fact causing a prolongation of acid clearance during sleep. The right lateral position during sleep causes more reflux episodes than the left lateral position. The gastroesophageal reflux may be associated with nocturnal wheezing, chronic nocturnal cough and sleep apnea.