How much sleep is enough?

How much sleep is enough?

In conjunction with Sleep Awareness week, Dr. Lim Li Ling, President of Singapore's Sleep Society, gives you a very comprehensive sleep guide--telling you what good sleep is all about with tips on how to sleep well.

How much sleep is enough?What constitutes good sleep or sleeping well?

Good sleep is sleep which is refreshing. A reliable indicator of adequate good quality sleep is waking up naturally feeling refreshed, and no excessive daytime sleepiness in the mid-afternoon.

How much sleep should I get every night?

Sleep needs vary with age. A newborn may need as much as 16-20 hours spread throughoutday, an infant may sleep 12-14 hours with most of sleep consolidated to the nocturnal sleep period, while toddlers may require 10 hours or more. Primary school going children should get 9-10 hours of sleep, while teenagers should get 8-9.5 hours. In adults, sleep requirement ranges from 6-10 hours. Although some people take pride in getting by with very little sleep, most people who get fewer than 5-6 hours of sleep are probably not getting enough sleep.

Aside from feeling rested and refreshed, are there other benefits from getting the recommended hours of sleep?

The purpose of sleep is believed to be rest and restoration for the mind and body, with lack of sleep affecting most profoundly, our brain functions. Once we have adequate amounts of good quality sleep, we should wake up feeling refreshed. This means that we can function mentally and physically at our peak potential. Regular good quality sleep greatly enhances quality of lifeand overall health, and allows us to perform our best.

How much sleep is too much? Is too much sleep bad for me?

It is unusual to be needing more than 10 hours of sleep a day. Too much sleep, like too little, is also associated with increased mortality. Some people who seem to need a lot of sleep mayhave an underlying primary sleep disorder such as obstructive sleep apnoea (OSA) or a much less common primary sleep disorder called “narcolepsy” characterized by excessive daytime sleepiness and sleep attacks.

A special group of people routinely sleep for longer than the usual 6-8 hours a night, they are called “long sleepers”, who routinely need more than 10-12 hours of sleep a day to feel refreshed. Notwithstanding, we do recommend that adult persons who have unusually prolonged sleep duration (needing more than 10 hours or sleep a day and still feeling tired) should seek medical attention, as this may be an indicator of underlying disease such as OSA.

How much sleep is enough?Some cultures advocate taking a short afternoon nap (“siesta”) – is this urge to take a nap normal, and should we give in to it when we can?

Feeling sleepy in the mid-afternoon is "physiological", i.e. it is part of the normal body clockfunction - we tend to feel sleepy at two times in a 24 hour day, mid-afternoon and at bedtime. In sleep deprived individuals who have not got enough sleep the night before (which happens quite often in modern fast-paced societies), taking an afternoon nap at the time to coincidewith this physiological mid-afternoon dip in alertness can be very refreshing. A short nap at that time helps us catch up on lost sleep, and leaves us feeling more alert and "recharged" for the rest of the day. Therefore a short afternoon nap is a good thing for people who generally tend not to get enough sleep at night because of their busy schedules.

Many adults have to work overtime and survive on 6 or less hours of sleep each day. What advice would sleep doctors give to such people?

Many people have hectic schedules and multiple demands on their time, a very common example being full-time working mothers with young children. For such people, finding time toget at least 6-8 hours of sleep seems impossible.

For such people, I would start with what I call “sleep education” i.e. letting them know that depriving oneself of sleep whatever the reason is in the longer term counterproductive because it exacts a significant toll on mental, emotional and physical health. Simply put, we become less effective, less efficient and increase our risk of serious diseases like heart disease, depression, diabetes and even early death if we persist in pushing ourselves to get by with less rest than we actually need.

It does not make very good sense to overwork ourselves when our health suffers inevitably as we deprive ourselves of sleep, the price we pay would be far too high no matter what “rewards” we get from pushing ourselves so hard at work. Our experience with patients is that once they truly understand what harm they do themselves when they shortchange themselves on sleep, they will find a way, by hook or by crook, to get more sleep on a daily basis. Education is key in order for people to make better choices for themselves.

Will sleeping more during the weekends help to make up for lack of sleep during the week?

Sleep debt is cumulative. The less sleep we get, we build up an increasing “pressure” to sleep until we are able to pay off this debt. Sleeping more the next day eg taking an afternoon nap, or sleeping in on weekends, are acceptable ways of paying off this sleep debt.

One common way to reduce the impact of sleep debt is to improve one’s alertness by using a stimulant, with caffeine being the most often used non drug substance. While this can keep one alert for several hours, it is not encouraged as a permanent solution to sleep deprivation,because ultimately sleep lack is associated with significant health risks, and the sleep debt needs to be paid off eventually somehow. Caffeine use is only a temporary measure.

Are there specific foods one should eat at dinner or near bedtime to induce sleep? Conversely, what foods should be avoided near bedtime?

Some foods which contain tryptophan, which is a precursor to serotonin (a neurotransmitter which is important for normal sleep), are often spoken of as being foods which help us sleep. Examples of food plentiful in tryptophan are milk, eggs, poultry and peanuts. Regardless of this theoretical basis for the touted benefit of such foods in promoting sleep, the real benefits are modest if at all.

We do not routinely recommend specific foods (except perhaps hot milk) to promote sleep, as this is not a particularly effective way to induce sleep. Conversely, certain food substances do actively interfere with sleep, such as caffeine and alcohol, and we routinely do discourage patients with sleep problems from drinking caffeine and alcohol too close to bedtime. As ageneral rule, in order to prevent acid reflux (the backflow of stomach acid -which is secreted after we eat in order to digest the food which has been eaten - up the food passage causing“heartburn” symptoms), patients are also discouraged from eating heavy meals too close to bedtime as well (i.e. within 2-3 hours of sleeping).

Does it matter what time we go to bed, as long as we get 7-8 hours of sleep?

It is most physiological or natural for adults to have their sleep consolidated into a single period of about 6-8 hours at night. This is because of our natural biological rhythms (or “circadian rhythm”) which determine when we are most sleepy, which is usually at night for most people, i.e. around 10-12 MN till about 6-8am for many.

Some people’s sleep phase is quite early or advanced, e.g. sleeping from 6pm till 2 or 3 am (“sleep early, get up early”) - usually older people; while some have delayed sleep phases, e.g.sleeping from 3am till 11am (“sleep late, get up late”) routinely – usually teenagers. As long as whatever sleep phase one has can fit in with their daytime social/occupational requirements, from a medical health perspective, it does not matter really what time we go to bed as long as we get the total amount of sleep we need.

I sleep 8 hours every night, but still wake up feeling tired and unrested. What could be thecause of this?

Unrefreshing sleep in spite of an adequate duration is usually suggestive of an underlying sleep disorder or mood disturbance, such as obstructive sleep apnoea (which is the blockage of the upper air passage during sleep, giving rise to symptoms of snoring and excessive daytime sleepiness because the frequent breathing disruptions during sleep prevent the person from getting consolidated, deep restorative sleep) or depression/anxiety. These are the mostcommon disorders causing unrefreshing sleep. If one feels tired and unrested in spite ofsleeping 8 hours every night, they are encouraged to consult a doctor for a medical evaluation.

What should we do to keep our brain in tip-top condition?

Getting enough sleep on a regular basis is one of the most important requisites for optimal brain functioning. The brain also needs a balanced diet, as nutritional deficiencies (eg. lack ofvitamins and other nutrients) can affect the nerve cell functioning. The brain also requires both physical and mental “exercise”. Regular robust physical exercise helps promote deep sleep, and also improves emotional wellbeing.

Mental activity includes continued learning which involves both sides of the brain ie in diverse subjects as language, science, creative arts like music, dance, art etc. Activities which engage both our physical and mental faculties simultaneously, such as dancing are especially beneficial for the brain, because they involve moving the body, and learning/memory such as remembering intricate sequences of dance steps.


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Tips For Better Sleep

1. Sleep-Wake Schedule: Go to bed and get up at about the same time every night and morning respectively, including weekends. Try to have a regular schedule of going to bed and waking up.This will help you to anchor your circadian (“biological”) clock and establish a consistent rhythm of sleep.

2. Bedroom Activity: Reserve the bed and bedroom only for sleep and sexual activity: Go to bed only when you are feeling sleepy. If you are not asleep after 20 minutes, then get out of the bed and engage in a relaxing activity outside of the bedroom like light reading or watching a (non-stimulating) television show. Go back to bed only when you feel sleepy again. Avoid using the bed for activities unrelated to sleep, eg. watching TV, reading, eating, studying.

3. Food & Drink: Avoid heavy meals within two hours of bedtime. Try not to go to bed hungry either. Avoid fluids close to bedtime to prevent awakening to go to the toilet. Avoid caffeine (which can stay in your system for up to 10-12 hours) after lunch and using alcohol as a sleepaid.

4. Bedtime Routine: Establish a relaxing pre-sleep routine while getting ready to go to bed, eg.reading, watching TV, listening to music. Set time aside to relax and practise natural relaxation techniques, eg. deep breathing, progressive muscle relaxation, visual imagery. Create and maintain an environment conducive to sleep, eg. comfortable bed and room temperature, darkness.

5. Napping: Avoid taking long daytime naps unless you are sleep deprived and are catching upon lost sleep. Afternoon naps, if taken, should not exceed 20 to 30 minutes.

6. Exercise: Regular physical exercise is encouraged because it promotes deep sleep, butvigorous physical activity should be avoided too close to bedtime. Do not engage in vigorous exercise within four hours before sleep.


Article by

Dr Lim Li LingPresident,

Singapore Sleep Society


Singapore Neurology & Sleep Centre, Gleneagles Medical Centre

More info check out the Singapore Sleep Society
Copyright (c) 123RF Stock Photos

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