Singapore - The myth of the 8-hour sleep

If you are tossing and turning every night fretting that you are not getting your full eight hours of beauty sleep, you are likely worrying for nothing.

The dogmatic idea that every adult has to get eight hours of sleep every night is likely a myth.

A sleep study on students published in the latest issue of the Eastern Economics Journal found that for older teens, seven hours a night was enough.

The study, which compared children's test scores with the amount of sleep they reported, revealed that 12-year-old did well on eight hours of sleep, and 10-year-olds required about nine hours of sleep.

US federal guidelines recommend about nine hours of sleep for children.

It appears that "no matter how much sleep children are getting, it has always been assumed that they need more," as summed up by a report by journal Pediatrics.

Experts YourHealth spoke to said the idea of the specific eight hour recommendation stems from the belief that after 16 hours of alertness, the body needs the remaining eight hours to rest and recharge.

However, this belief, which has since become somewhat of a dogma, can be misleading.

"Some people may fret unnecessarily if they are not getting the full eight hours, and the stress it creates is undesirable," said Dr Lim Li Ling, President of Singapore Sleep Society and Medical Director of the Singapore Neurology & Sleep Centre.

People should not be fixated on the idea that they must get eight hours of sleep, as every individual is different, she added.

Taking herself as an example, Dr Lim said she needs seven hours of sleep every night. For most adults, the number of hours required falls between six to eight hours. For newborns, sleep requirement may go as high as 16 hours.

However, doctors interviewed warned against the idea that you can just copy your neighbour in sleeping four hours a night and be in the pink of health.

While different people may have different sleep requirements, Dr Lim says it generally settles around the eight hour mark, give or take an hour or two.

"There is an elite that by virtue of nature, don't need much sleep,"  Prof Michael Chee of the Duke-NUS Graduate Medical School and Principal Investigator of the Cognitive Neuroscience Lab told YourHealth.

"Mutations in hDEC2 confer such ability in perhaps the one to three per cent of persons who get by on four to five hours a night," he said.

"However, just as most of us don't have the athletic chops of a professional athlete or the body of a model, we'll need more to stay in top shape."

What's the ideal sleep requirement?

According to Prof Chee, this is similar to asking "what is the best diet". There is no simple answer to this question.

Research simply shows that dogmatic time recommendations may not be necessarily correct, he said.

While in one study, researchers were surprised to find that students on 7 hours of sleep fared no worse in scholastic achievement than those on 9 hours, another study on 12,000 subjects found that students with less than 8hours of sleep were more likely to engage in risky sexual behavior and consume tobacco.

In addition, differing lifestyles play a part in determining the amount of sleep we need, he said.

"Sleep loss increases the rate of performance decline as you persistently engage in an attentionally demanding task. So if you are just vegetating, you probably won't notice sleep loss as if you are making many decisions on a complex plan," he said.

A good gauge of your sleep requirement is how many hours of sleep you consistently need to feel well-rested, Dr Lim advised.

If you are crawling out of bed every morning, or drinking a cup of coffee every morning, you are likely sleeping below your requirements.

Indications that you have hit your requirement includes:

>> Waking up naturally

>> Feeling refreshed

>> Able to sustain alertness

>>Having no urge for a nap

>> Not requiring artificial stimulants like coffee.

Fragmented sleep: Good or bad?

As recent reports have cast doubt on the veracity of the number eight, some say the myth could extend as far as suggesting a continuous eight hour sleep is 'unnatural'.

A report by BBC suggested that it is normal to get two sleep sessions - one in the early evening, and another later in the night after a break.

Historian Roger Ekirch said much of historical evidence shows that humans used to sleep in two distinct chunks.

Later on in history, attitudes changed to encourage a full eight hour block of sleep, but while most have adapted to this sleeping pattern, Ekirch believes that the human body's natural preference for segmented sleep as well may be the root of many sleeping problems.

This includes a condition called sleep maintenance insomnia, where people wake during the night and have trouble getting back to sleep.

The anxiety cause by the 'false' belief that humans need to sleep in a consolidated block could lead to a vicious cycle, Ekirch said.

However, experts here say this is no reason to go against the recommended full eight hours every night, and especially not to support the practice of waking up in the middle of the night to surf the net, only to complain of feeling tired the next day.

If you are waking up in the middle of the night naturally, there is no reason to get overly anxious and take unnecessary steps to remedy it, such as taking sleeping pills.

This is medically unsound, Prof Chee said.

However, whether polyphasic sleep is necessarily better is another question. This is as the body goes through several stages of sleep every sleep cycle, from light sleep to the deeper stages of stage 3 non-REM and REM sleep.

Rapid eye movement (REM) sleep first occurs about 90 minutes after falling asleep, and may last as long as 10 minutes to an hour.

If you are awoken after entering the deeper sleep cycles, you may experience sleep paralysis or 'sleep drunkedness', Dr Lim said. In a worse case scenario, you may feel groggy for the rest of the day, affecting your work productivity.

And while some research has suggested that an afternoon nap may be beneficial, Dr Lim said that this is taking into consideration that most of us are sleep deprived, and an extra half-an-hour shut eye is beneficial as an addition to the total amount of sleep time.

Another factor to consider that a continuous block of sleep is simply more time efficient. While Dr Lim conceded that the retired or children can afford to sleep in small chunks, most of us have schedules that would just 'not make sense'.

Kei Yamada

YourHealth, AsiaOne

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