Swallowing Mystery: Why We Don't When Asleep

Have you ever wondered if you swallow in your sleep? It's a common question, and one that has been the subject of scientific study. It turns out that we do indeed swallow during sleep, but it happens mostly during the REM, 1 and 2 stages of sleep, and is associated with movement arousals. This means that there are long swallow-free periods during sleep. Interestingly, the urban legend that we swallow spiders in our sleep is just that—a myth. Spiders tend to avoid humans due to our size and the vibrations we create through noises like breathing and heartbeat.

Swallowing is episodic during sleep, with long swallow-free periods

Swallowing during sleep is episodic, with long intervals between swallows. This was discovered in a study of 10 subjects, where sleep was staged using EEG, EOG and EMG, and swallowing was monitored by an external sensing device attached to the neck. The study found that swallows occurred almost exclusively in association with movement arousals, which are most frequent during the REM, 1 and 2 stages of sleep.

The study also found that swallowing during sleep is episodic, meaning there are periods of sleep where no swallowing occurs, followed by periods where swallowing occurs multiple times. This pattern of swallowing during sleep is thought to be influenced by the sequential and orderly activation of swallowing muscles, which is monitored by the laryngeal excursion during deglutition.

Although influenced by sensory and cortical inputs, the sequential muscle activation does not alter from the perioral muscles caudally to the cricopharyngeal sphincter muscle. This provides evidence for the existence of a central pattern generator for human swallowing. The brain stem swallowing network includes the nucleus tractus solitarius and nucleus ambiguus, with the reticular formation linking synaptically to cranial motoneuron pools bilaterally.

Under normal function, the brain stem swallowing network receives descending inputs from the cerebral cortex, which may trigger deglutition and modulate the brain stem sequential activity. The voluntarily initiated pharyngeal swallow involves several cortical and subcortical pathways. However, the interactions of regions above the brain stem and the brain stem swallowing network are not yet fully understood, particularly in humans.

Swallowing occurs with movement arousals during the REM, 1 and 2 sleep stages

A study conducted by Lichter et al. in 1975 investigated the pattern of swallowing during sleep. The study involved 10 normal subjects, and their sleep was staged using EEG, EOG, and EMG, with swallowing monitored by an external sensing device attached to the neck.

The study found that swallowing during sleep is episodic, with long swallow-free periods. Interestingly, swallowing occurred almost exclusively in association with movement arousals, which are most frequent during the REM, 1, and 2 sleep stages. This means that during the deeper sleep stages, the body experiences longer periods without swallowing.

The REM stage of sleep is when your eyes move rapidly and your brain is active, similar to when you are awake. Dreams typically occur during this stage. Non-REM sleep, on the other hand, consists of three stages where your brain is less active, and your heart rate and breathing slow down as you progress through them.

The first stage of non-REM sleep is when your eyes are closed, but you can be easily woken up. This light sleep phase usually lasts for 5 to 10 minutes. The second stage is deeper, with slower heart rate and breathing, and a drop in body temperature as the body prepares for deep sleep. This stage can last from 10 to 25 minutes. The third stage is deep sleep, during which it is harder to wake the sleeper, and they would feel disoriented if awakened.

To summarise, while we do swallow during sleep, it happens infrequently and is associated with movement arousals, particularly during the REM, 1, and 2 sleep stages.

Spiders are unlikely to enter a sleeping person's mouth due to vibrations from heartbeat and breathing

Spiders are highly unlikely to enter a sleeping person's mouth. While the idea that we swallow eight spiders a year has become ingrained in popular culture, it is not based in fact. There are several reasons why spiders are unlikely to enter a sleeping person's mouth. Firstly, humans are extremely large compared to spiders, so we are more likely to be viewed as part of the landscape.

Secondly, and most importantly, a wandering spider would find a sleeping human terrifying due to the vibrations caused by our heartbeat and breathing. Spiders are extremely sensitive to these vibrations, and they would likely avoid us as a result. The chances of a spider entering your mouth while you sleep are so slim as to be negligible. If a spider did crawl onto your face while you slept, the sensation of its legs on your skin could wake you up very quickly.

The myth that we swallow spiders in our sleep likely originated in a 1993 magazine article as an example of how readily people accept information they read online as fact, even if it seems ridiculous. In reality, only a small number of spider species share our homes, and most of these prefer seclusion. They tend to live in webs in quiet corners or areas where humans don't spend much time, such as basements and attics.

Swallowing is a complex motor event, challenging to investigate in humans

Swallowing is a complex motor event that is challenging to investigate in humans. The act of swallowing involves the coordination of more than 25 pairs of muscles in the mouth, pharynx, larynx, and oesophagus. The process of deglutition can be divided into three phases: oral, pharyngeal, and oesophageal. The oral phase is voluntary and is controlled by cranial nerves V, VII, and XII. The pharyngeal phase is involuntary and is controlled by cranial nerves V, VII, IX, X, and XII. The oesophageal phase is also involuntary and is controlled by the oesophageal striated muscles. The act of swallowing is initiated by stimulating a nerve, namely, the internal branch of the superior laryngeal nerve.

Swallowing is a fundamental motor activity that serves two vital functions: it propels food from the oral cavity into the stomach and protects the upper respiratory tract by preventing the pulmonary aspiration of food particles.

The brain stem swallowing network includes the nucleus tractus solitarii and nucleus ambiguus with the reticular formation linking synaptically to cranial motoneuron pools bilaterally. The swallowing network can be viewed as a linear-like chain of neurons based on the rostrocaudal anatomy of the swallowing tract. The sequential firing of dorsal medullary neurons during swallowing has been recorded.

The act of swallowing is episodic during sleep, with long swallow-free periods. Swallows occur almost exclusively in association with movement arousals, which are most frequent during REM, 1 and 2 stages of sleep.

Sleep studies use EEG, EOG, and EMG to monitor swallowing and sleep patterns

Sleep studies are a crucial tool for understanding sleep patterns and diagnosing sleep disorders. They involve conducting multiple tests simultaneously during sleep to measure specific characteristics. One such test is electroencephalography (EEG), which measures brain wave activity and provides a summary of electrical activity from one area of the brain. This is particularly important for differentiating between the various stages of sleep.

Another test used in sleep studies is the electrooculogram (EOG), which records eye movement. Eye movements can indicate the stage of sleep an individual is in, with rapid eye movement (REM) sleep being characterised by rapid eye movements. The EOG is crucial for differentiating REM sleep from other stages.

Additionally, electromyography (EMG) is employed to measure muscle movement and tone. This test helps distinguish between the various stages of sleep, particularly when differentiating REM sleep from other stages. Together, these three measures—EEG, EOG, and EMG—provide valuable insights into an individual's sleep patterns.

In a study investigating the pattern of swallowing during sleep, these three measures were utilised. The study found that swallowing during sleep is episodic, with long swallow-free periods. Swallows were observed to occur almost exclusively in association with movement arousals, which are most frequent during REM, Stage 1, and Stage 2 sleep.

By monitoring an individual's brain wave activity, eye movement, and muscle tone with EEG, EOG, and EMG, sleep studies can provide a comprehensive understanding of sleep patterns and help diagnose and treat sleep disorders.

Frequently asked questions