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More BODY CLOCKS going out of synch

Circadian rhythm sleep disorders - when sleep timings do not coincide with the 24-hour natural rhythm of the body - are under-recognised here, even as sleep clinics handle more patients in recent years
The Straits Times - March 15, 2012
By: Joan Chew
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Deep in the inner recesses of the brain lies a master clock that governs many functions of the body.

The circadian rhythm, often called the body clock, follows a roughly 24-hour cycle and determines one's sleeping and feeding patterns, among others.

Someone may be a 'morning person' or 'night owl', depending on his natural tendency. His circadian rhythm is further influenced by his activities and the amount of light he is exposed to, which affects the level of a sleep hormone called melatonin.

But therein lies the problem for people whose work and other commitments put them out of synch with their body clocks. To fulfil such societal obligations, they cannot afford to awake or sleep spontaneously.

The result is sleep deprivation and impaired functioning.

What many people do not realise is that this is a serious health issue and not just a matter of coping with less sleep, said neurologist Lim Li Ling, president of the Singapore Sleep Society.

The society looks to correct this misconception with its week-long campaign which starts tomorrow on World Sleep Day.

Dr Lim, a sleep specialist at Gleneagles Medical Centre, said: 'We hope to raise awareness of the silent epidemic of sleep-related disorders which can have serious mental and physical health implications.'

The long list of consequences arising from not getting enough or quality sleep includes depression, behavioural problems, obesity, high blood pressure, heart disease, as well as accidents and loss of work productivity due to impaired attention and vigilance. Affected children can suffer from impaired growth and poor school performance.

In the last few years, sleep clinics in public hospitals here have been seeing 10 to 40 per cent more patients.

The number of patients seeking help for sleep disorders at the Singapore General Hospital (SGH) increased 40 per cent from 2,400 in 2008 to 3,400 last year.

The National University Hospital (NUH) has also seen a year-on-year increase of 8 to 13 per cent in the past three years. These numbers are expected to continue to increase with Singapore's ageing population and the rising number of people with medical conditions which disrupt sleep, said Dr Lim.

Most of those who seek help have obstructive sleep apnoea - when the airway becomes blocked during sleep, causing frequent pauses in breathing which wake them up.

What seldom gets treated, however, are circadian rhythm sleep disorders, which tend to be under-recognised.

Dr Lim has handled only about five cases a year since 2004. She said such patients usually seek her help only after exhausting their supply of sleeping pills and are at their wits' end because they can barely function at work due to sleep deprivation.

Fewer than five in 100 patients in a sleep clinic are in this group, estimated Dr Chua Ai Ping, a consultant at the division of respiratory and critical care medicine at NUH.

No one knows how many more people are untreated. Those whose lifestyle can be adjusted to fit their abnormal sleep patterns require no help, but treatment is needed for those who cannot do so and lack sleep.

The most common type of circadian rhythm sleep disorder is jet lag, which is experienced when someone travels across time zones. Half of all travellers are known to have jet lag, said Dr Sridhar Venkateswaran, assistant director of Changi General Hospital's integrated sleep service medicine.

How bad symptoms such as insomnia and daytime sleepiness are and how long they last vary, depending on the number of time zones crossed, the direction of travel, the journey's timing and other patient factors.

Although jet lag is the most common, it is usually temporary.

What is more insidious is the long-term effect of shift work on employees such as airline crew and hospital staff, who grapple with misaligned clocks on a regular basis.

The 2011 Singapore Yearbook of Manpower Statistics reported 18 per cent of employees here work shifts, with the majority working in hotels and restaurants.

Overseas studies show that up to two-thirds of shift workers fall asleep on the job at least once a week. They are also twice as likely to have a work-related accident.

It has also been observed that shift workers have higher rates of obesity, heart disease and gastro-intestinal disorders.

Aside from extrinsic factors, life changes such as puberty can also predispose a person to a circadian rhythm sleep disorder known as delayed sleep phase syndrome.

A study of students in six schools here in 2008 found that four in five teens were not getting the optimal eight to nine hours of sleep on school nights. Half were getting only five to six hours.

Dr Jenny Tang, a paediatrician at Gleneagles Medical Centre, said changes in the hormonal profile at puberty comes with a delay in bedtime by an average of two hours.

A teen's tendency to be glued to his computer screen till the wee hours aggravates a delayed sleep phase. An adult too can be guilty of this.

This becomes a disorder when it affects the quantity and quality of sleep.

Needing a caffeine boost to start the day or stay awake, afternoon naps and sleeping in on weekends point to insufficient sleep.

The key to good sleep starts with good habits, said Dr Lim.

She said: 'No doctor is needed to treat voluntary sleep deprivation. As in the case of exercise, once a person realises the importance of sleep, he will usually find time for it.'

Habits which promote good sleep include not engaging in mentally stimulating activities, such as watching TV in the bedroom, and avoiding heavy meals, alcohol, caffeine and smoking before bedtime.

While it is all right to catch up on sleep during the weekends, do not sleep in more than two hours beyond your usual wake-up time so as not to disrupt the internal clock.

Doctors usually advise those suffering circadian rhythm sleep disorders to make use of light to adjust their internal clocks.

Exposure to light in the evening shifts the clock to a later time. Similarly, light exposure in the morning shifts it to an earlier time.

When these strategies are insufficient, melatonin is prescribed to induce sleep at a desired time, which then gradually realigns the circadian rhythm over time.



Circadian rhythm sleep disorders are related to the timing of sleep within the 24-hour day. People with such disorders do not have a problem maintaining sleep once they are asleep, but their sleep-wake routine is out of synchronisation with the norm.

This is a problem only if they are required to sleep or wake up at times that disrupt their sleep cycles, so they do not get enough or good quality sleep. It can lead to symptoms such as insomnia, fatigue and excessive daytime sleepiness.

The circadian rhythm is affected by light exposure, the levels of melatonin - a sleep hormone - in the body and the activities that one engages in.



The person has a natural circadian rhythm that is shorter than 24 hours, leading to his bedtime becoming earlier and earlier over time.

This syndrome results in sleepiness in the evening and the early onset of sleep so the person awakens in the early hours of the morning.

It is often brought on by age and is fairly common among the elderly.

It is not an issue if the person can adjust his lifestyle to match his sleeping hours - which is easier to achieve if he has retired from work.



This is the opposite of advanced sleep phase syndrome. People with this syndrome - typically adolescents and young adults - tend to feel sleepy later and later.

It is usually caused by performing mentally stimulating activities and exposure to light at night.

They may not be able to fall asleep until the wee hours of the morning, which makes it difficult for them to wake up in time for school and work.



This results from a person crossing time zones too rapidly for the body's circadian clock to keep pace. The body clock remains aligned to the home environment.

The adjustment process is often slow, averaging about one hour of phase alignment per day after east-bound flights and 1.5 hours per day after being on west-bound flights.

So symptoms can last several days. Morning larks report less jet lag than night owls when travelling east, but the latter group does better when travelling west. Young travellers and those who exercise regularly suffer less jet lag than those who are older and sedentary.



At night, a person's body temperature falls to its minimum just before he goes to sleep. The body also produces more melatonin, the body's natural sleep hormone, at night.

Working at night goes against natural sleeping patterns.

So people who frequently rotate shifts or work at night may develop shift work sleep disorder.

After a night of work, they may find it difficult to sleep during the day because of daytime noise, bright sunlight and social obligations, such as attending to their children's needs.



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