Sleep disorders do not affect only eye health. It is estimated that 30 per cent of other chronic diseases are also related to sleep issues.
Clinical studies have shown that sleep deprivation affects brain function, said Dr Toh Song Tar.
He is director of the sleep disorders unit and consultant in the department of otolaryngology at Singapore General Hospital.
When a person is sleep-deprived, it affects his thinking abilities and emotional states, Dr Toh said.
The person cannot concentrate well, yawns frequently and is generally more irritable than usual.
Lack of sleep also limits a person's ability to learn and affects his memory. When someone is sleep-deprived, the effects of alcohol consumption are magnified, as is his risk of being involved in an accident, added Dr Toh.
A lack of sleep can also make a person short-tempered and subject to mood swings. Sleep deprivation can trigger mania episodes in people who have manic depression. Other risks include impulsive behaviour, depression, paranoia and suicidal thoughts.
Sleep deprivation can also cause microsleep. This is when the person nods off for a few seconds, up to 30 seconds, without realising it.
This can be dangerous if the person is driving, said Dr Toh.
Microsleep can also make a person more prone to injuries from trips and falls.
Studies show that sleep deprivation also weakens the body's immune system, so a person falls sick more easily and recovers from illnesses more slowly than others.
If someone already has a chronic lung disease, sleep deprivation is likely to make it worse, said Dr Toh.
Long-term sleep deprivation raises the risk of developing chronic conditions such as diabetes and cardiovascular diseases, he added.
Some studies have also found a link between lack of sleep and weight gain.
Sleep deprivation increases the production of the stress hormone cortisol, and lowers the levels of a hormone called leptin, which tells a person's brain that he has had enough to eat.
Weight gain leads to higher risks of chronic health problems such as high blood pressure, heart disease and stroke, said Dr Toh.
Overall, studies show that the risk of death from all causes goes up by 15 per cent if a person sleeps fewer than four hours a night. Doctors should be aware of the harm that sleep disorders can cause.
Routine clinical examinations should include asking patients about their sleep, said Dr Toh.
Snoring, for instance, is a sign of airway obstruction.
It will cause damage to the upper airway tissue because of repetitive tissue trauma, leading to swelling and the tissue becoming more flaccid, he said.
This will lead to the development of more obstruction and eventually obstructive sleep apnoea, which is the more common type of sleep apnoea.
Sleep apnoea is a potentially serious sleep disorder in which breathing repeatedly stops and starts.
Many people see the doctor only after they have been snoring for many years and, by then, the damage may have been done.
If a person snores every night with choking, gasping episodes, has unrefreshing sleep and excessive daytime sleepiness, he should see a doctor for evaluation, said Dr Toh.
Ng Wan Ching
•World Sleep Day on March 18 will focus on important issues related to sleep through recognition, better prevention and management of sleep disorders.