Sleepwalking: the consequence of poorly regulated deep sleep?

In France, around 2% of adults are affected by somnambulism, a slow deep sleep disorder that is characterized by motor activity during the night, even while the person is asleep. The fact that this parasomnia is infrequent contributes to its ignorance, but a study published on June 24, 2021 in the journal Frontiers in Neurology gives new keys to try to understand it better.

The overworked parasympathetic nervous system

A group of Canadian and American researchers wanted to go further in the already advanced hypothesis according to which sleepwalking is due to a disturbance of slow deep sleep, a phase in which the person is difficult to wake up and where the rhythm of breathing and the heart becomes more regular. They recruited for the study 14 sleepwalkers and 14 other people not suffering from this disorder, to constitute a control group. Their sleep was assessed by video-polysomnography – an examination which records several physiological variables such as heart and respiratory rhythms – overnight, after 25 hours of sleep deprivation.

Result: it could be observed that the autonomic nervous system of sleepwalkers differs from that of others. The autonomic nervous system regulates vital functions such as breathing, smooth muscles and even heart muscles. It is made up of sympathetic system, which manages the automatic functions of the body, and parasympathetic system, which slows them down and allows energy to be stored. Contrary to what one might think, it is the latter which is over-solicited in sleepwalkers.

“A new and broader way to understand biological processes”

“While the causes of sleepwalking remain unclear, we do know that while sleeping, sleepwalkers can experience an abnormal interaction between wakefulness-related processes and deep sleep, even outside of their episodes., explain Antonio Zadra and Andrée-Ann Baril, co-authors of the study. In other words, sleepwalkers may present evidence of both wakefulness and deep sleep; a condition from which episodes of sleepwalking can occur. Our results indicate that compared to healthy adults, the autonomic nervous system of sleepwalkers promotes their parasympathetic activity during sleep. This opens a new and broader way to understand the biological processes involved in sleepwalking.”

According to the researchers, however, it remains to “determine if and how this atypical activity is involved in the occurrence of actual sleepwalking episodes”. But in view of these observations, “since several pharmaceuticals can be used to modulate the effects of the autonomic nervous system, such treatments could be explored if our findings are replicated and expanded”, They conclude.