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Although the subject of ‘sneezing during sleep’ has not been extensively studied, most sleep researchers and neuroscientists agree it is physically impossible for people to sneeze while they are sleeping.
For all intents and purposes, humans should sneeze frequently during the night. Our mucus membranes swell when we lie on our back, stomach, or side; swollen mucus membranes are a common cause of sneezing. However, the body suppresses sneezing impulses through a process known as rapid-eye movement (REM) atonia, which occurs during certain periods of sleep. The neurotransmitters that normally detect allergens and other irritants shut down during REM atonia, thus preventing the involuntary urge to sneeze.
Sneezing, also known as sternutation, refers to the involuntary expulsion of air from the lungs through the nose and mouth. Most sneezes occur due to irritants affecting nasal mucus; sneezing essentially cleans out the nose and throat when these irritants are detected.
The biological process for sneezing is as follows:
Sneezing utilizes muscles and muscle groups throughout the body. Common causes for sneezing include:
Sneezing is rarely dangerous. However, the expulsion can produce up to 40,000 aerosol droplets that can spread infectious diseases. For this reason, physicians urge people to cover their mouths and nose when sneezing, and to wash their hands with soap and water after the sneezing has subsided.
Sleep in humans is facilitated through an internal timekeeper known as the circadian clock. The circadian clock is based on natural sunlight. A sleep-inducing hormone called melatonin is released at night once the sun goes down; then, in the morning, the melatonin tapers off and the sleeper feels more alert.
Following the circadian rhythm, the sleep cycle in humans is composed of five distinct stages: four stages of non-REM sleep (75% of the cycle) and one stage of REM sleep (25% of the cycle).
The first five-stage cycle lasts roughly 90 minutes, and successive cycles last 100 to 120 minutes. As a result, humans may experience anywhere from four to seven sleep cycles per night.
As we discussed earlier, REM atonia — which exclusively occurs during Stage 5 — causes all neurotransmitters to shut down. As a result, the motor neurons that trigger sneezing are not stimulated, regardless of whether or not the sleeper’s nasal cavity is exposed to irritant particles.
If REM atonia prevents sneezing during Stage 5, then why don’t we sneeze during the other four stages of the sleep cycle? This is where the science gets tricky. In the non-REM stages, two parts of the brain — the thalamus and cerebral cortex — activate one another in order to suppress sensory reactions such as sneezing. However, excessively strong stimuli can still trigger sneezing responses. When this occurs, the sleeper will wake up and then sneeze. So while we do not sneeze while sleeping, we are still susceptible to the sneeze reflex during the non-REM stages and may wake up as a result.
Sleepers can exercise the following precautions before going to bed in order to curb the need to wake up due to sneezing during the night: