Sleep is an essential function that allows your body and mind to recharge, leaving you refreshed and awake.
But one thing that can disrupt your sleep are known as parasomnias, or abnormal events or experiences associated with sleep. Think sleepwalking and night terrors.
According to Dr Ari Manuel, respiratory, sleep and ventilation consultant for Spire Healthcare and Liverpool University Hospitals NHS Foundation Trust, these are "more common" than people think, and the symptoms may not be obvious.
Most people don't seek help for these problems because “firstly, because they don’t understand the disorder and, secondly, because they don’t feel that doctors can help,” explained Dr Manuel.
Many of these events are thought to be caused by poor sleep quality, which may be a result of sleep disorders such as sleep apnea.
Here are some of the most disturbing sleep disorders to be aware of.
Sleepwalking
Sleepwalking, also known as somnambulism, is more common in children.
They may have their eyes open, speak, or otherwise appear awake, but will not recall the episode the following morning.
Dr Manuel said: "There may be a genetic link as it can run in families. Some people make their way back to bed while others wake up."
Sleepwalking can be relatively harmless, although if are suddenly woken, they are likely to be shocked and disorientated.
Night terrors
Night terrors are different to nightmares, which occur in REM sleep.
In around 80% of cases there’s a family history, yet most children grow out of them by adulthood, explains Dr Manuel.
This can occur at the same time as sleep walking, where people to try escape from something. They can be inconsolable but have no memory of the experience.
Experts advise monitoring safety and guiding the sleeper back to bed once they calm down.
Confusional arousal
If someone wakes up too quickly from deep sleep they may be slow to respond, can't think clearly or may be frightened.
Dr Manuel said: "The person is disoriented but it tends to wear off quickly.
"Sleep apnoea can be an underlying issue and if that is treated effectively, this deals with the confusional arousal."
Sexsomnia
Sexsomnia is a rare condition that has only just been recognised as a parasomnia.
It refers to sexual activity occurring when the subject is asleep, and unaware of their action.
Like other disorders, triggers include lack of sleep, exhaustion, drug and alcohol use, stress, anxiety, travel or simply sharing a bed with someone.
‘Exploding head’ syndrome
This is when a person hears or feels a very loud noise, described as “a painless loud bang”, “a clash of cymbals” or even “a bomb exploding”, usually just before falling asleep or waking.
The most likely explanation is that there is some kind of temporary blip in the nerve cells of the brain.
Sleep paralysis
Those who experience sleep paralysis describe being unable to move muscles while dropping off or waking up.
It’s thought to occur because the person is in “sleep mode” while the brain is active.
In many cases, there may also be visual, auditory and tactile hallucinations with the person seeing figures or animals, hearing footsteps or feeling pressure on their body or the bed. They may also feel as though they are floating or being lifted up.
Episodes can last from a few seconds to several minutes and can end either spontaneously or because of an intense effort to break the paralysis or by the touch or voice of another person.
REM behaviour disorder (RBD)
“Usually, our bodies are paralysed during dreams and we don’t act them out,” explains Professor Walker.
“In those with REM sleep behavioural disorders the mechanism in our brain that paralyses our body fails.”
So, if a person is dreaming of running, they will thrash their limbs as if they are running. Many people aren’t aware that they’re acting out their dreams until their bed partner notices it, or worse, ends up with bruises.
The disorder can occur at any age but is more likely to affect men over 50.
