General Sleep & Health, Normal Sleep Requirement

Why is sleep important to good health?
Sleep is a vital time of rest and restoration of the body. Sleep deprivation leads to physical and emotional adverse consequences on health. These include reduced attention and vigilance, with daytime sleepiness – leading to accidents, elevated blood pressure, mood disturbances, increased risk of obesity, heart disease and reduced lifespan.

What are signs of excessive sleepiness?
Excessive daytime sleepiness refers to the inability to stay alert in daylight hours. This is often due to sleep deprivation, and sometimes related to sleep disorders which reduce the quality and duration of nocturnal sleep. Signs include nodding off, yawning, drooping eyelids and reduced attention.

What are signs of not enough sleep?
Signs include excessive daytime sleepiness, disturbed mood (eg. Feeling depressed and irritable), reduced attention and vigilance (leading to accidents at tasks which require attention and vigilance such as driving) and headaches.

What is the ideal amount of sleep that one should get?
Sleep needs vary with age. A newborn (0-3 months) may need as much as 14-17 hours spread throughout day, an infant (4-11 months) may sleep 12-15 hours with most of sleep consolidated to the nocturnal sleep period, while toddlers (1-2 years) may require 11-14 hours of sleep. Preschoolers (3-5 years) need 10-13 hours of sleep. Primary school going children (6-13 years) should get 9-11 hours of sleep, while teenagers (14-17 years) should get 8-10 hours. In adults, sleep requirement ranges from 7-9 hours. Older adults (65+ years) need 7-8 hours of sleep. 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.(Source: National Sleep Foundation Sleep Duration Recommendations 2015)

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, ie. around 10pm to 12 midnight till about 6 to 8am for many. Some people’s sleep phase is quite early or advanced, eg. sleeping from 6pm till 2 or 3 am (“sleep early, get up early”) – usually older people; while some have delayed sleep phases, eg. sleeping from 3am till 11am (“sleep late, get up late”) routinely – usually teenagers. As long as whatever sleep phase one adopts can fit in with their daytime social or occupational requirements, from a medical health perspective, whether we are early birds or night owls can be acceptable as long as we get the total amount of sleep we need.

What Is Good Sleep?
You are a good sleeper if you fall to sleep and wake up at about the same time every day, including weekends. You should get at least 6 to 8 hours of sleep on a regular basis. When you wake up, you feel refreshed and can maintain normal alertness throughout the day. It is normal to feel a mid-afternoon “dip”, but there should not be overwhelming sleepiness. Toward bedtime, you know how to relax yourself after a busy day, and fall asleep within 10 to 15 minutes of going to bed. You do not wake up except once or twice to go to the bathroom, and fall back to sleep easily. Good sleepers reap the benefits of feeling invigorated in the morning and are poised to make the most of their innate abilities, whether it be at school or at work. Adequate sleep allows us to perform to the best of our abilities, unimpaired by fatigue, mood disturbances and poor concentration or thinking.

What are the consequences of not having sufficient sleep?
Lack of quality sleep affects alertness most immediately, with daytime sleepiness and increased risk of accidents (eg. driving, operating machinery on the job) being an immediate consequence. This impaired mental function, with diminished attention and vigilance, leads to poorer school and work performance. The brain is most immediately and severely impacted by sleep loss. Over time, there are physical health consequences as well. These include increased risk of heart disease, weight gain, tendency to develop diabetes, depression, and ultimately a shorter lifespan. In children and adolescents, lack of sleep impairs normal growth and development, leads to behavioural disturbances and more mood disorders like depression.

What are the negative effects of not having enough sleep?
Enough good quality sleep is essential for physical and emotional well being. Enough sleep, regular exercise and a balanced diet are the basic triumvirate of good physical and emotional health, basic prerequisites for looking and feeling our best. Chronic lack of sleep increases our risk of diseases such as heart disease, diabetes, obesity, and depression, as well as shortens our lifespan. Overall not having enough sleep is a stressful state which increases our risk of diseases associated with ageing.

There are times when I find it difficult to sleep. What could be causing this?
The most common reasons for difficulty falling or staying asleep are psychological, such as excessive stress, depression or anxiety. Often lifestyle factors contribute to poor sleep, such as working, eating or exercising late into the night, taking substances which adversely affect sleep close to bedtime such as caffeine, alcohol or smoking, or having poor sleep habits, such as irregular sleep-wake times. Sometimes medical conditions such as chronic pain and side effects of common drugs (eg. asthma medication, steroids) can be a cause of insomnia. People who have difficulty sleeping should seek medical attention to determine the cause, so that appropriate treatment can be given, which is dependent on the underlying cause. Routine or long term use of sleeping pills, without proper identification of the cause of insomnia, is not recommended.

Aside from feeling rested and refreshed, are there other benefits from getting the recommended seven to eight 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. The amount of sleep in normal healthy adults ranges from around 6 to 10 hours, some require more, others less. 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 life and overall health, and allows us to perform our best.

Are there any natural techniques or supplements that can assist me when I’m having difficulty sleeping?


Healthy sleep habits are a basic prerequisite to good sleep. These include having a regular sleep-wake schedule, regular exercise, good stress management techniques, avoiding the excessive use of substances such as caffeine, alcohol and nicotine, and having a regular wind-down routine prior to bedtime. Non-drug methods to improve sleep include cognitive behavioural therapy – changing thoughts and behaviours non-conducive to sleep (eg. tossing and turning in bed when unable to sleep, watching the clock, drinking caffeine or smoking near bedtime) and natural relaxation techniques (eg. deep breathing, visual imagery). Most “supplements” are not well studied and there is no compelling evidence for the benefits of traditional medication or “natural” supplements for insomnia. Melatonin is often tried for insomnia, though the evidence suggests that it is mainly useful for the insomnia related to circadian rhythm sleep disorders such as jet lag. Lavender is a herb with an aromatic fragrance which has been used in scents, soaps, teas and bath oils. The claim that it has soothing, calming or sedating effects has not been well-supported by robust clinical studies, with only isolated reports in alternative medicine journals of its use in insomnia. Similarly there is no good evidence for the use of Chamomile tea as a sleeping aid. As such, sleep doctors who practice evidence-based medicine do not routinely recommend the use of herbal products such as these in the treatment of insomnia.

How much 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 may have an underlying primary sleep disorder such as obstructive sleep apnoea (OSA) (blockage of the upper air passage during sleep) or a much less common primary sleep disorder called “narcolepsy” characterized by excessive daytime sleepiness and sleep attacks. Some people normally routinely sleep for longer than the usual 6 to 8 hours a night – such people are called “long sleepers”. Long sleepers routinely need more than 10 to 12 hours of sleep a day to feel refreshed. Nothwithstanding, it is recommended that adult persons who have unusually prolonged sleep duration (needing more than 10 hours or sleep a day and still feeling tired) seek medical attention, as this may be an indicator of underlying disease such as OSA.

What affects one’s sleep quality?
Physical and psychological factors can affect quality of sleep. Physical factors include bright light/darkness, room temperature, quiet/noise, and physical problems like pain, shortness of breath, discomfort of any kind eg. itch. Psychological factors include stress, anxiety, depression, excitement/anticipation. Anything which keeps us in a high arousal state – whether it is a physical factor (eg. husband snoring, or noisy TV sounds, or room too cold or hot), or psychological (eg. worrying, anxious about next day exams or interview) – can cause overstimulation which affects our quality of sleep. Medications can also disrupt sleep quality, some medications like steroids or asthma drugs can cause alertness as a side effect which prevents us from sleeping soundly, adjusting the timing of such medications may help.

Overall sleep quality is affected by a variety of factors:
1. Sleeping at regular times is important. A chaotic sleep-wake schedule is detrimental to sleep because it disrupts our body’s internal clock which regulates our normal sleep wake cycles.
2. Sleeping environment is important. This should be dark and quiet and at a temperature conducive to sleep.
3. Stimulating drugs and substances such as alcohol, nicotine and caffeine can disrupt sleep and should be taken appropriately timed away from bedtime. Alcohol should not be used as a sleep aid. Caffeine should be avoided from the afternoon hours to late at night.
4. Long afternoon naps, or sleeping in too long on weekends both can affect our nocturnal sleep. Both should be avoided.
5. Medical disorders which cause excessive physical or psychological arousal can affect sleep. Examples are chronic pain, heart failure, asthma, depression and anxiety.
6. Primary sleep disorders (there are over 90) can affect sleep quality in a variety of ways, causing sleep disruption and usually a range of complaints such as insomnia, daytime sleepiness or abnormal movements in sleep. Patients with poor quality sleep should consult a physician if this is affecting their health or quality of life.

I find myself yawning during the day even though I have 8 hours of sleep. Why is this so?
Feeling sleepy in spite of getting 8 hours of sleep may indicate that one is not getting enough sleep on a regular basis, or that the sleep quality is poor. If one is sleeping 8 hours regularly (which should be an adequate amount for most adults) and still feeling sleepy in the daytime, it could be an indication that there is a primary sleep disorder causing poor sleep quality. Examples of sleep disorders which cause daytime sleepiness are obstructive sleep apnoea, where there is sleep related breathing disturbance, or narcolepsy, which is a rare condition in which people have irresistible sleep attacks in spite of sleeping enough hours at night. A consultation with a sleep specialist is suggested, and a sleep study (where the quality of sleep, and factors contributing to sleep disruption) may be needed.

Is there such a thing as sleeping too much? What is the optimum amount of sleep for an adult?
Although it is commonly believed that getting “8 hours” of sleep is optimal for health, large population studies have shown that people who get 8 or more hours, or less than 4 hours of sleep, have higher death rates than those who average 6 to 7 hours of sleep. So “8 hours” of sleep is no longer touted as the ideal sleep duration. Sleeping for long hours, yet waking unrefreshed, may be a sign of a primary sleep disorder, which is affecting the quality of sleep.

The amount of sleep we need varies according to age. In adults, there is a wide range of about 6 to 10 hours. There are people who can sleep fewer than 5 hours and still function normally, this group of people is known as “short sleepers”. However most people will require at least 6 hours of sleep a night. Conversely, at the opposite end are the “long sleepers” who may routinely need 10 to 12 or more hours of sleep. Most people will need 6 to 8 hours of sleep daily.

Infants, children and adolescents need much more sleep. For example, infants need up to 15 hours of sleep a day in the first year of life. Children need up to 11 hours of sleep and adolescents need at least 8 to 10 hours of sleep for optimum functioning. A simple way to gauge the amount of sleep needed is to recall one’s sleep pattern during vacation time when there are no external pressures dictating when we go to bed and when we have to get up. During such times when we allow ourselves to fall asleep and wake up naturally, we should feel refreshed and alert in the daytime. Our normal sleep requirement can be estimated from such non-stressful times.

Conversely, when we are not getting enough sleep, we tend to feel very sleepy in the daytime, and fall asleep very quickly at bedtime. Sleep deprived people have difficulty getting up in the morning without an alarm clock, and often have to sleep in over the weekend to catch up on lost sleep accumulated over the week. If your sleep pattern is such, then you likely are not getting enough sleep on a regular basis.

What are the common problems that will arise with constant staying up late at night? (Will it really increase our risks of getting heart related disease and cancer?)
Staying up late at night on its own is not directly harmful to one’s health, unless doing so and then getting up early the next day prevents us from getting the amount of sleep that we need. Lack of sleep, or sleep deprivation, which may arise from regular late nights, and getting up at the usual time for a normal work day, is definitely associated with health risks. Chronic partial sleep deprivation can lead to depression, weight gain, a tendency to diabetes, high blood pressure and heart disease. These are well established in scientific research. The causal link to cancer is less well established, but there are reported associations between lack of sleep and tumours.

Does staying up late really pose health problems or it doesn’t really matter as long as the duration of sleep is long enough?
As above, staying up late is not as much of a problem as the duration and quality of sleep. Lack of adequate good quality sleep can cause many health related problems as listed above.

What is your advice for people who need to stay up late constantly?
General advice applies, get enough good quality sleep on a regular basis – if you lose sleep because of late night work, try to make up for it the next day, or at least, over the weekend. In general it is healthy to have a regular sleep-wake schedule, so the internal (“circadian”) biological clock can stabilize. So eg. working the night shift is not as much of a problem if it is permanent, because the body clock adjusts to the same schedule of working through the night, and sleeping during the day. Overall it is healthier and more natural (physiological) to sleep at night and work in the daytime, so if staying up late is a lifestyle choice (eg. for social reasons, or a habit) rather than a necessity because of work requirements, adjusting one’s sleep pattern would be ideal. A healthy sleep pattern is one which is regular, relatively fixed and stable, and sleep occurs mainly at night.

Does the duration matter if the quality of sleep is good?
Yes. Each person has an individual requirement of sleep duration which is healthy. In general babies and children need much more sleep, up to 11-15 hours a day. Adult sleep requirements vary between 6-10 hours, most people need at least 6-7 hours of sleep a night.

Is there a way to minimize the side effects that a lack of sleep may cause to health?

The “sleep debt” that builds up when we do not get enough sleep must be paid off to prevent adverse effects on health. Many people drink coffee to keep going even when they are sleep deprived. While this may temporarily improve alertness, this does not help the detrimental effects of sleep deprivation on health, such as mood changes and increased blood pressure. So there is no other way than to catch up on lost sleep by taking naps or sleeping in on weekends. Taking short naps after a night of lost sleep helps reduce the side effects.

If we lack sleep for one night, does sleeping more the next night or during the day help?

Yes, catching up on lost sleep the next day, or even the weekend after a cumulative week of lack of sleep are helpful to repay the “sleep debt”.

I sleep with the air-conditioner on. If it turns off in the middle of the night, I automatically wake up, even though the room is still cool. Why is this so?
One reason could be that the noise of the air-conditioner serves as a form of “white noise”, which is a soothing sound in the background, which can help lull one into sleep. Once this sound is turned off, a light sleeper may be sensitive to the change and hence wake up.

What is the optimum room temperature (if any) for sleeping?
The optimum temperature for sleeping is whatever the person prefers. Some like it warm, some cool, others very cold. The ideal environment for sleeping is that which is quiet, dark and the ambient temperature whatever is most comfortable for the individual.