What is sleepwalking?
A sleep behavior being partially awake (performing wake like behaviors) and partially asleep (no recollection of the event).
It is also called "somnambulism" and "nocturnal wandering".
What triggers sleepwalking?
Current data suggest a physiological rather than a psychological origin. In other words it doesn't seem to be caused by some mental issue but rather by a less than perfect balance of functions in the brain during sleep.
Sleep is composed of different phases with current data suggesting that different parts of the brain are in different sleep phases at any defined sleep time. Sleepwalking could be due to some parts of the brain being awake when they should not be, thus triggering some physical activity but no memories of it.
Who is affected?
This is hard to tell for sure (see next paragraph) and you most likely won't know until there is someone witnessing your sleep, one way or another.
But according to this study the lifetime prevalence in the adult US population is 29.2%.
Limitations of current sleepwalking data.
Most if not all sleepwalking data available in the scientific/medical literature have been obtained in 1 of 2 different ways:
1/ through interviews of sleepwalkers and/or of someone from their immediate surrounding (partner, parent, co-inhabitant, etc...)
2/ through nights spent at a sleep clinic where sleep and body functions were monitored through video and polysomnography
Those data have provided invaluable understanding of sleepwalking and of potential treatments for it. But because of the way those data are collected objective correlations and longitudinal data are not available, which are key for further understanding sleepwalking.
1/ Data collection through interviews is limited to what the interviewee can remember and won't provide a complete picture but only one of the events that are marking enough to wake them up. For example this method of collection selects for the most intense sleepwalking events and will miss events minor enough to not awake anyone. Moreover potential triggering factors mentioned in the scientific/medical literature have been provided by the sleepwalker as 1 time factor (had a drink that night, had a tense moment that day, etc...) and have not been tested through repetitive measurements to verify that they are indeed the trigger for that particular person.
2/ Sleeping in a different environment than the regular one, with half a dozen probes attached to the head, chest and legs and knowing that someone is watching you through a camera for the entire night cannot trigger the same sleep pattern as happening in a regular sleep environment. So here also this approach will yield data representing only part of the situation: in that case behavior strong enough to occur in an unfamiliar environment but most likely not the more subtle behavior that would provide a complete picture.
What would be the ideal sleepwalking data collection?
Probably a combination of tools to record the behavior and physiological activities of a sleepwalker in a familiar environment without affecting its comfort.
Being a sleepwalker I am working on this approach and part of this blog's aim is to share the data I obtained, which I believe would help at least expand the discussion on what is sleepwalking and what can be done about it.