There are many kinds of sleep disorders.
Large studies abroad show that about one in five people reports having sleep issues.
The prevalence should be the same here, said Dr Leow Leong Chai, a consultant in the department of respiratory and critical care medicine at Singapore General Hospital (SGH).
He gives a brief rundown of the various sleep disorders.
CIRCADIAN RHYTHM DISORDERS
These are conditions in which the body's biological clock has been disrupted, leading to unstable or undesirable sleep-wake cycles.
On top of delayed sleep phase disorder or the "night owl" syndrome commonly seen in some teenagers, these disorders also include jet lag and shift-work disorder.
Jet lag is caused by travelling to different time zones before the body has time to adapt.
Shift-work disorder happens when those doing night shifts find it hard to stay awake at night and sleep during the day.
Today, more people are also staying up late to play computer games, watch videos and movies, or communicate via their smartphones. This can disrupt their body clock .
OBSTRUCTIVE SLEEP APNOEA (OSA)
This is a condition in which a person wakes up many times in the night because of snoring and intermittent stoppage of breathing.
Causes include narrowing of the airway at the back of the throat and behind the tongue during sleep.
This can be due to obesity, tonsillar enlargement or having too small an upper or lower jaw.
If untreated, OSA not only leads to poor sleep and excessive daytime sleepiness, but also raises the odds of developing or worsening heart disease, stroke and hypertension .
The most common and effective treatment for OSA is to use a continuous positive airway pressure or CPAP device, which involves wearing a pressurised mask over the nose or mouth during sleep to keep the upper airway open.
These include sleep walking, sleep talking and dream enactment. They are uncommon conditions which often run in the family but are also sometimes associated with neuro-degenerative conditions, such as Parkinson's disease.
Alcohol intake, stress or sleep deprivation can trigger these episodes.
Management of these conditions includes avoiding these triggers and, in severe cases, medication.
One in five people complains of being unable to sleep or of waking up frequently at night.
Tackling this problem involves identifying and treating issues such as sleep apnoea, excessive noise or light, and practising good sleep habits, such as having a fixed bed time and avoiding caffeine four hours before going to bed.
RESTLESS LEGS AND PERIODIC LIMB MOVEMENT DISORDERS
Sufferers complain of uncomfortable, painful, cramping, itchy or often hard-to-describe sensations in the lower limbs associated with an urge to walk or shake the limbs, in the evening and before bedtime.
These sensations can be severe enough to cause insomnia and, even if the person is asleep, can persist and cause periodic shaking of a limb and subsequent sleep disturbance.
Management involves identifying and treating any underlying causes such as iron deficiency and nerve diseases. In severe cases, effective medications are available.
This is a rare condition caused by a deficiency of a special hormone in the brain which is required to regulate sleep and wakefulness.
This condition commonly shows up in teenagers as overwhelming sleepiness to the extent of falling asleep while eating or having a conversation, despite having an adequate amount of sleep during the night.
Narcoleptics may also experience dream-like hallucinations and cataplexy, which are brief episodes of generalised loss of muscle tone triggered by laughter or surprise.
It is treated with medications that promote wakefulness or with strong stimulants.
Ng Wan Ching