Understanding Human Reflexes During Sleep

Sleep is a restorative process that allows the body to recuperate, repair, and rest. During this time, various reflexes and involuntary actions continue to occur, albeit under different conditions compared to when we are awake. This article explores the common questions about whether humans sneeze, cough, or hiccup while sleeping.

The Mystery of Sneezing While Asleep

Indeed, it is widely believed that humans do not sneeze during sleep. This is primarily due to the intricate neurological processes that govern our responses. When awake, sneezing is an involuntary reflex triggered by the sensory neurons in the nasal mucosa. These neurons detect irritants and send signals to the brain, which then initiates a series of actions to expel the irritant.

However, when we sleep, particularly during rapid eye movement (REM) sleep, certain neurotransmitters are tightly regulated, leading to a state known as REM atonia. This condition causes motor neurons to shut down, preventing the initiation of sneezing or any other voluntary actions. Consequently, while the nasal mucosa may be more sensitive when lying down, the lack of external stimulation reduces the likelihood of sneezing.

In some instances, external stimuli can still trigger a sneeze reflex, but the reflex is often followed by waking up.

Coughing and Hiccuping During Sleep

Coughing and hiccuping, like sneezing, are reflexive actions that are more likely to occur during lighter stages of sleep. Unlike REM sleep, the brain remains relatively active during non-REM sleep, especially in the earlier stages. This lower level of sleep can allow for the body to respond to irritants, triggering a cough or a hiccup.

For example, if one sleeps with the mouth open, external stimuli such as dust or gases can trigger a cough. Similarly, the diaphragm contraction associated with hiccups can also occur during sleep, although it is typically brief.

Individual Sensitivities and Sleep

Some individuals sleep very lightly and are highly sensitive to external stimuli. For them, a slight sound or a change in air pressure may be enough to trigger a reflex action like sneezing or coughing. However, for most people, these reflexes are not common during deep sleep due to the brain's reduced activity during this stage.

It is important to note that while rare, it is theoretically possible for reflexes to occur even during deep sleep. However, the probability is much lower.

Conclusion

While it is rare for humans to sneeze, cough, or hiccup during deep sleep, these reflexes can still occur under certain conditions. Understanding the neurological processes involved in these reflexes can help clarify why they are less common during sleep and provide insights into the different stages of sleep and their physiological implications.

For further reading, you may wish to explore topics such as the sleep cycle, neurological processes during sleep, and the differences between REM and non-REM sleep.