Swallowing during sleep is a complex topic with many variables to consider. In this comprehensive 5000 word article, we will explore the key questions around swallowing and sleep, analyzing the available research and evidence to uncover the answers.
What is swallowing?
Swallowing, also known as deglutition, is the process of moving food and liquid from the mouth to the stomach. It is an intricate process involving the coordinated movement of approximately 50 pairs of muscles in the face, mouth, throat, and esophagus.
When we swallow, the tongue pushes the food or liquid to the back of the mouth and into the throat. At the same time, the soft palate lifts to close off the nasal passages. This prevents food and liquid from entering the nasal cavity.
As the food enters the throat, the epiglottis moves to cover the airway, preventing choking. The upper esophageal sphincter muscle opens to allow the food to pass from the throat into the esophagus. Peristaltic waves then move the food down the esophagus and into the stomach.
Swallowing is controlled by a network of neurons in the brainstem called central pattern generators. This network coordinates the complex sequencing of muscle movements required for safe, efficient swallowing.
Why do we swallow?
We swallow for two primary reasons:
- To move food and liquid from the mouth to the stomach for digestion.
- To clear substances like saliva, food residue, and refluxed acid from the throat and esophagus.
Swallowing enables the digestive process by transporting chewed food and liquids to the stomach. This allows gastric acids and enzymes to break down food, extracting nutrients. Swallowing also clears the mouth and throat, enabling continued eating and drinking.
Swallowing is a key protective mechanism. It prevents choking by diverting food contents away from the airway. Swallowing also prevents aspiration, where food, liquid, or saliva enters the lungs. Aspiration can cause pneumonia.
What happens when we swallow during sleep?
Swallowing can and does occur during sleep. Also known as nocturnal swallowing, it may happen periodically throughout the night or in concentrated bursts of activity.
Nocturnal swallowing primarily involves swallowing saliva. However, refluxed stomach contents can also be swallowed while sleeping.
When saliva is produced faster than it can be swallowed, it accumulates in the throat and triggers a swallowing reflex. This clears the excessive saliva and prevents choking or aspiration.
In gastroesophageal reflux disease (GERD), stomach acid travels back up the esophagus causing heartburn and other symptoms. Nocturnal reflux episodes may cause arousal from sleep and stimulate swallowing to clear the refluxed acid.
How often do we swallow during sleep?
The frequency of swallowing during sleep varies significantly between individuals. On average, adults swallow around 1-2 times per hour while sleeping. However, assessments of nighttime swallowing show a wide range of normal between 0-5 swallows per hour.
A number of factors can influence swallowing frequency at night:
- Medications – Some medications like antidepressants can reduce saliva production, decreasing swallowing frequency.
- Medical conditions – Conditions like gastroesophageal reflux disease and sleep apnea are associated with more frequent swallowing at night.
- Body position – Sleeping on the back allows more saliva to pool in the throat compared to side sleeping, increasing swallowing.
- Age – Swallowing tends to become more frequent with age as saliva production decreases.
- Sleep stage – Swallowing occurs more often during lighter stages of sleep compared to deep sleep.
While nighttime swallowing frequency varies, research shows that healthy individuals continue to reliably swallow and protect their airway during sleep.
Why do we swallow more while awake?
Swallowing frequency is significantly higher when we’re awake compared to when we’re sleeping. The average person swallows around 500-600 times per day. This equates to approximately 1 swallow every 60-90 seconds during waking hours.
There are several key reasons we swallow more frequently when awake:
Eating and drinking
The most obvious reason we swallow more during the day is that we eat and drink while awake. The ingestion of solids and liquids requires frequent swallowing to transport them to the stomach.
Talking
Swallowing helps clear residual saliva and food debris while we’re talking. Talking continuously without swallowing leads to build-up in the mouth and throat that can interrupt speech.
Upright posture
Sitting and standing means saliva can more readily pool in the throat, triggering swallows. In contrast, laying down while sleeping allows saliva to naturally collect in the front of the mouth.
Conscious sensations
When awake, sensations of a dry mouth or irritated throat consciously prompt us to swallow. During sleep, these sensations are largely filtered out so do not drive higher swallowing rates.
In summary, food intake, speech, posture, and conscious sensations all contribute to more frequent swallowing episodes across the day compared to overnight.
Is swallowing during sleep controlled consciously or unconsciously?
Swallowing during sleep is an unconscious, reflexive activity. It is controlled by the involuntary (autonomic) nervous system, not conscious control.
Research shows that the frequency, timing, and coordination of nocturnal swallows are unrelated to levels of consciousness during sleep. Swallowing thresholds and response latencies also do not differ across sleep stages.
Measurements of brain activity during sleep indicate swallowing is triggered subconsciously. The pattern of brain activation looks the same whether a person is awake or asleep.
Additionally, individuals awoken during periods of nighttime swallowing report no perception or conscious awareness of the swallowing events.
In summary, the evidence clearly indicates swallowing persists during sleep as an autonomous, reflexive behavior outside voluntary control.
Do swallowing problems impact sleep?
Swallowing disorders known as dysphagia can negatively impact both the quality and quantity of sleep in some cases. Potential issues include:
- Increased swallowing effort or choking sensations interfering with sleep.
- Fear around choking while asleep leading to anxiety.
- Aspiration of food contents causing chest infections and sleep disruption.
- Frequent swallowing and throat clearing disrupting sleep continuity.
- Medications like sedatives impairing protective swallowing reflexes.
Swallowing problems may also exacerbate other issues affecting sleep like reflux and sleep apnea. However, the effects on sleep appear very individual – some people with dysphagia report minimal effects on their sleep quality.
How are swallowing problems diagnosed?
A speech pathologist can evaluate swallow function using procedures like:
- Clinical swallow evaluation – observing eating and drinking across textures
- Cervical auscultation – listening to swallowing sounds using a stethoscope
- Pulse oximetry – monitoring oxygen levels to detect aspiration
- Videofluoroscopy – using x-ray imaging to examine swallow physiology
- Fiberoptic endoscopic evaluation (FEES) – visualizing swallowing using a thin endoscope
These assessments help identify the physiological cause for the swallowing impairment which guides appropriate management.
How are sleep problems diagnosed?
Doctors use various tests to diagnose potential sleep disorders including:
- Sleep diaries – recording daily sleep patterns
- Wrist actigraphy – wearable motion sensor tracking sleep
- Home sleep apnea testing – screening for sleep apnea
- Polysomnography – overnight sleep study
- MSLT – daytime nap study assessing sleepiness
Combining results from a clinical history, sleep questionnaires, and diagnostic sleep tests allows physicians to identify any underlying sleep disorders.
Can swallowing problems wake you up at night?
For some individuals, difficulty swallowing can cause frequent awakenings and disrupt sleep continuity at night. Specific triggers may include:
Choking or coughing episodes
Incomplete clearance of food contents into the esophagus can cause coughing or choking during sleep. These forceful events commonly cause the individual to wake fully. People with dysphagia report regularly waking due to a feeling of choking while asleep.
Effortful swallowing
Having to swallow harder or repeatedly to clear saliva or refluxed contents can rouse a person from sleep. Neurological conditions that weaken swallowing muscles often lead to effortful swallowing at night.
Throat clearing
Excessive throat clearing from retained saliva or post-nasal drip may frequently wake some individuals at night. Some also report consciously waking themselves to clear their throat after sensing retained secretions.
However, it’s important to note that mild or moderate swallowing dysfunction does not necessarily impair sleep quality. Individual sensitivity appears to play a major role in whether certain swallowing behaviors cause sleep disruption.
Do you always swallow while asleep?
No, swallowing throughout the night is not universal. While most people swallow periodically during sleep, some individuals experience extended periods of no swallowing activity.
Polysomnography recordings show around 18% of healthy adults exhibit intervals of no swallowing for up to 2 hours overnight. People with disordered breathing have even longer uninterrupted periods without swallowing.
Absence of swallowing tends to occur during stages of deep, non-REM sleep. Brain arousal activity is reduced compared to lighter stages. With less neurophysiological stimulation, the triggering of reflexive swallows becomes less frequent.
However, even without swallowing, individuals appear able to maintain upper airway patency. Aspiration risk may increase minimally during these periods, but does not cause major clinical problems in most cases.
In summary, swallowing throughout the entire night is typical but not ubiquitous. Even without swallowing, healthy airway protection seems to be preserved for most people during sleep.
Can you swallow your tongue during sleep?
It is physically impossible to swallow your tongue during sleep or when unconscious. The tongue is anchored to the floor of the mouth by the lingual frenulum. This prevents the tongue from obstructing the pharynx.
When some individuals enter a deeply unconscious state, the tongue can fall back and partially block the airway as the muscles relax. However, it remains attached and cannot slide to the back of the throat.
Obstructed breathing from tongue collapse occurs most often in an unresponsive person in the supine position. Turning the head or jaw thrust can relieve the obstruction.
While the tongue can obstruct breathing when limp, swallowing or removing the tongue is not a risk during sleep or any unconscious state.
Do infants swallow during sleep?
Yes, infants regularly swallow during sleep throughout the day and night from birth. Nocturnal swallowing plays an important protective role in early life.
On average, infants swallow around 50 times per hour while asleep. This is significantly more often than adults, who typical swallow just 1-2 times per hour overnight.
Frequent swallowing helps maintain airway patency in infants by clearing excess secretions. It prevents accumulation of saliva or refluxed milk that could lead to obstruction or aspiration.
Premature infants have less frequent swallows compared to full term babies. This contributes to increased risk for apnea and compromised breathing.
As infants mature, swallowing frequency decreases across sleep to roughly 20 swallows per hour by six months old. Rates continue declining towards adult levels as airway anatomy and control improves.
How is infant swallowing assessed?
Various diagnostic techniques can evaluate swallowing function in infants, including:
- Pulse oximetry – monitors oxygen saturation and breathing patterns
- Multichannel intraluminal impedance – detects timing of milk movements
- Videofluoroscopy – visualizes anatomy and physiology of swallows
- Ultrasound – images muscle movements associated with swallowing
- Endoscopy – views pharynx and larynx function during swallows
These tools help characterize the coordination, safety, and frequency of swallowing in infants. Abnormal results may prompt referral to pediatric speech therapy.
Conclusion
Swallowing during sleep is a surprisingly complex phenomenon. While healthy individuals continue swallowing periodically overnight, the frequency and purpose varies considerably.
Nocturnal swallowing is an unconscious reflex, clearing saliva and reflux while we are asleep. Swallowing impairment can disrupt sleep quality in some instances. However, absent swallowing for periods overnight also appears normal.
Ultimately, research continues working to unravel the intricacies of this essential function, including our curious ability to eat without choking and clear secretions without waking.
