What Is Sleepwalking?

Introduction

Have you ever considered what happens when someone is sleepwalking? Is it because their spirit has gone out of their body? If not, then what is the mechanism behind this action? 

Sleepwalking, also known as somnambulism, occurs when individuals engage in movements and actions while in a state of sleep. During these episodes, individuals often appear detached from their surroundings, displaying limited responsiveness and typically retaining no memory of the sleepwalking incident. These episodes predominantly manifest during the initial one-third of a person's sleep cycle and are thought to result from disrupted sleep patterns and abnormal brain activation, often attributed to underlying pathological or psychological factors.

Sleepwalking is not often reported and noticed and is not recorded as a cause of serious injuries or hospitalisation, representing its low prevalence. Sleepwalking is more frequent in childhood rather than adulthood. In this article, we will take a closer look at sleepwalking.

Sleepwalking basics

Before we discuss the principles of sleepwalking, here are some basics of sleeping. It is interesting to know What We Do When We Sleep. We experience two types of sleep every night, rapid eye movement (REM) sleep and non-rapid eye movement (NREM) sleep, they cycle repeatedly every night. NREM sleep is when sleepwalking often happens. When we are prepared to lie in bed, eyes closed, we will first enter NREM sleep. 

NREM sleep can be divided into three stages: 

• The first stage of NREM sleep is the first type of sleep we experience. During the first stage of NREM sleep, your body calms down, heart rate and breath rate decrease, and muscles relax.¹  The brain wave transits slowly from wakefulness to a lower-voltage, mixed-frequency wave. 
• The second stage of NREM sleep follows the main pattern of the first stage, but you would need stronger stimuli to awaken. Your eye movements tend to stop, and your body temperature decreases. The brain activity continues to slow down with certain patterns called sleep spindles and K-complexes, which are related to memory consolidation during sleep.²
• The third stage of NREM sleep, or sometimes combined with the fourth stage of NREM sleep, takes up the largest percentage of your first sleep cycle.¹ At the end of this stage, high-voltage, slow-wave activity emerges, representing the body relaxing into deeper rest. 

REM sleep occurs after NREM sleep and around 90 minutes after you sleep. Dreaming often occurs in REM sleep but can happen during the NREM period. REM happens under your eyelids, and your brain wave activity returns closer to the pattern when you are awake. Your heart rate and breath rate also slightly increase compared to NREM sleep. But your muscles will lose their tone and flexibility, just like being paralyzed. This is a state called atonia, which prevents people from acting out their vivid dreams.² 

Symptoms and behaviours

Sleepwalking behaviours include basic wake-up and walking, either with eyes opened or closed, and not responding to others, but they may mutter some sentences to themselves. In some extreme circumstances, people may do their routine activities, leave the house, and even behave unusually or violently. People who sleepwalk may find it difficult to wake up during their sleepwalk and have limited memory of the episode the next morning.³

Causes and triggers

Sleepwalking often takes place during NREM sleep, initiated during slow-wave sleep (SWS), known as deep sleep, which is when our brain activity tends to relax into deep rest.⁴ Sleepwalkers are characterised by the inability to maintain steep and stable slow-wave sleep, with arousals during the SWS period shown on their electroencephalograms (EEG). While the exact mechanisms are not fully understood, sleepwalkers may exhibit unique sleep patterns, including incomplete arousals, rather than a simple inability to maintain stable slow-wave sleep.

With sleepwalking, the body is prepared to enter NREM sleep. Blood flow reduces in the brain regions that control our conscious awareness and behaviours.⁴ The sensory functions are ready to switch off, so some sleepwalkers do not feel pain or other senses during this period. However, a study from the University of Zurich showed that in sleepwalkers, brain regions like the brainstem and cerebellum, related to motor function and sensory processing, remain active, hence leading to potential movements.⁵

One of the significant triggers of sleepwalking in adults is disturbed sleep due to stress, anxiety and depression.⁶ In other cases, medication and neurodegenerative disorders can affect sleep quality, leading to sleepwalking. A literature review has collected medications affecting neurobiology during sleep, which potentially trigger sleepwalk as a side effect. They’ve reviewed four classes of drugs: benzodiazepine receptor agonists, antidepressants, antipsychotics and β-blockers.⁷

The role of genes in sleepwalking is unclear, but genes controlling our circadian rhythms, like CRY and PER, affect our sleep. Some other genes that are inheritable may be responsible for familial sleeping disorders.¹ 

Diagnosis and evaluation

Because of its special occurrence timing, it is hard to observe sleepwalking when patients are alone. A sleep diary or partner’s log of events may be useful to record sleep quality and abnormal behaviours.⁸ In clinical settings, questionnaires serve as diagnostic tools for conditions like sleepwalking and other disruptive sleep-related disorders. These questionnaires encompass questions about alcohol and medication consumption, medical background, event timing and characteristics, as well as family history.⁸ 

Polysomnography is the only reliable method of measuring sleepwalking.9 Polysomnography is a study that measures your sleep pattern; parameters like heart rate, brain waves, and eye and leg movement are recorded for your sleep profile. During the test, you may be referred to a sleep centre where you will stay overnight or complete the test in your house. The sleep centre room has a low-light digital camera for the technologist to see the room. Before you sleep, electrode sensors will be attached to your body parts with wires connected to machines. If you are doing the test in your home, you will do it according to instructions and provide a sleep log afterwards.¹⁰ However, this method is not recommended as it is not cost-effective and convenient to measure random and infrequent behaviours like sleepwalking. 

Differentiating sleepwalking from other sleep disorders

Distinguishing NREM and REM parasomnia is important as they require different interventions. Sleepwalking as an NREM sleeping disorder usually happens in one’s early years and is “outgrown” by young adulthood. However, REM sleeping disorders are more likely to appear in one’s later years and are associated with underlying neurological conditions such as Parkinson’s disease. REM sleeping disorders include REM sleep behaviour disorder, sleep paralysis and nightmare disorder. Patients with REM sleeping disorders are responsive to awakening, and they can remember the events that happened during sleep, unlike those with NREM sleeping disorders.⁸

NREM sleeping disorders themselves have their distinguishable characteristics as well. Sleep terror and sleep-related eating disorders are also NERM sleeping disorders. Sleep terror is marked with screams and cries, while sleep-related eating disorder always involves food-seeking behaviour.⁸

Sleepwalking in children

As previously mentioned, sleepwalking is more common in children and adolescents. Data reveals that up to 45% of children aged 4-16 have experienced sleepwalking, but it is infrequent among children, with only 2-3% reporting incidents happening once per month. The hypothesis of sleepwalking in children relates to the growth and development of their brains. The wiring of neurons in the brain changes and grows, and this maturation process may trigger certain patterns of behaviour during sleep.¹¹ 

Treatment and management

There is no current cure for sleepwalking and some may suggest no treatments are required because it causes no major problems for sleepwalkers. However, interventions must be taken to prevent injuries or violent behaviours. Providing a safe sleeping environment could reduce the chance of injuries, like locking windows and external doors to prevent falling from windows or exiting the house, also removing vulnerable objects around sleepwalkers to minimise the risk of injury.⁹ 

There were no clinical trials to prove the efficacy of treatments, but case reports have shown that scheduled waking or hypnosis may be promising treatments. Hypnosis provided by healthcare professionals leads patients to a relaxed state where they reduce awareness of their surroundings and increase focus on themselves.¹²  Records in adults aged from 18 to 50 who underwent hypnosis have reduced or no sleepwalking after the assigned treatment period. Scheduled waking means waking the patient 15-30 minutes earlier than the time they sleepwalk and ensuring they are fully awake for some time.³

Other interventions with several successful cases include acupuncture and aversion therapy, but not enough cases were recorded.¹³ Medications are not intended to treat sleepwalking but to reduce the frequency of sleepwalking episodes. According to the NHS, Benzodiazepines or antidepressants are sometimes used for patients with high sleepwalking frequency or with a high chance of hurting themselves and other people.¹⁴ 

So, should you ever wake up someone while sleepwalking? The suggested method to handle sleepwalking cases is to ensure their safety and gently guide them back to bed. Restraining and shouting at the person is not recommended unless they are in danger, as they may react with a fight or flight response.^14,15

Summary

To summarise, sleepwalking is a condition where patients get up from bed, move around, and perform an action while they are asleep. Sleepwalk usually happens during NREM sleep, around the first to third cycle of our sleep. Children have a higher chance of experiencing sleepwalking than adults but it will eventually disappear as they grow up. Sleepwalking in adults may be caused by stress, anxiety, depression, medication or underlying neurological conditions. Sleepwalking puts pressure on patients themselves and their partners. It affects patients' daily lives and may cause sleepiness during the daytime. For sleep partners, it's stressful to be disturbed by patients. 

Although there is no cure for sleepwalking, hypnosis and scheduled waking are the two main treatments for sleepwalkers. It is important to seek professional evaluation and care, especially when sleepwalking leads to injury and violence.