Yes, humans swallow while sleeping, though less frequently than when awake. Swallowing is a complex reflex action that serves to clear the throat and move substances from the mouth into the esophagus. This involuntary process is fundamental for maintaining an open airway and managing oral secretions.
The Act of Swallowing During Sleep
Swallowing during sleep is primarily an involuntary, reflexive action, differing from conscious, voluntary swallowing. While awake, adults typically swallow about once per minute, or roughly 500-700 times a day. During sleep, this frequency decreases significantly, dropping to approximately once every 5-10 minutes, or around three times per hour. This reflex is coordinated by a network of neurons in the brainstem, specifically the medulla oblongata. This brainstem activity helps manage the movement of saliva and mucus, ensuring these substances are directed away from the airway.
Factors Influencing Sleep Swallowing
Reduced swallowing frequency during sleep is influenced by several physiological changes. Different sleep stages play a role, with less frequent swallowing occurring in deeper sleep stages. For instance, studies indicate that swallowing activity is minimal or absent during Stage N3 (deep sleep). As the body enters sleep, muscle relaxation extends to the throat muscles involved in swallowing, contributing to the decreased swallowing rate.
Another influence is the reduced production of saliva during sleep, which follows the body’s natural circadian rhythm. With less saliva accumulating, the need for frequent swallowing lessens. The autonomic nervous system also regulates aspects of swallowing during sleep, allowing for necessary protective reflexes.
The Role of Saliva and Mucus
During sleep, the primary substances being swallowed are saliva and mucus, which are continuously produced in the mouth and throat. Saliva, composed mostly of water, contains enzymes, mucus, and antibacterial compounds that moisten the mouth. Mucus also helps trap foreign particles and keeps membranes moist.
If these fluids were not swallowed, they would accumulate, leading to issues like drooling, a common occurrence resulting from reduced swallowing frequency and relaxed facial muscles. Even infrequent swallowing during sleep helps prevent the excessive buildup of these secretions, which could otherwise interfere with breathing or lead to aspiration into the lungs. This protective mechanism remains functional to maintain airway clarity.