Healthy sleep

What is it?

According to MedlinePlus: sleep is a natural process that helps the body restore its energy, supports learning and memory, and keeps you healthy. All the stages of sleep are necessary for healthy sleep.

NHLBI defines sleep deprivation as a state that occurs when you do not get enough sleep. Sleep deficiency is broader, and occurs with one or more of the following: not getting enough sleep, sleeping at the wrong time of day, not sleeping well or not getting all the types of sleep the body needs, or having a sleep disorder that prevents enough sleep or makes it poor quality.

NHLBI also explains that the body has a biological clock with a rhythm that usually repeats every 24 hours, and that "sleep pressure" builds with every hour you spend awake. Light and darkness help determine when you are awake and when you are sleepy, while exposure to bright artificial light late in the evening can make it harder to sleep.

Why it matters

The CDC says that getting enough sleep helps you: get sick less often, stay at a healthy weight, lower stress and improve mood, improve heart and metabolic health, lower the risk of chronic diseases such as type 2 diabetes, heart disease, high blood pressure and stroke, reduce the risk of car accidents, and improve attention and memory.

MedlinePlus states that the stages of sleep allow the heart and blood vessels to rest, growth hormone is released during them to support growth and tissue repair, sleep helps balance the hunger and fullness hormones, and it helps the immune system produce substances that fight infection.

According to NHLBI, sleep deficiency is linked to many chronic health problems, including heart disease, kidney disease, high blood pressure, diabetes, stroke, obesity and depression. It adds that it can cause physical and mental health problems, injuries, lower productivity and a higher risk of death.

NHLBI explains that sleep deficiency causes blood sugar to rise above the normal level, which may raise the risk of diabetes, that too little sleep raises the level of the hormone ghrelin and lowers leptin so that you feel hungrier, and that a person with sleep deficiency may find it harder to resist common infections. Sleep deficiency has also been linked to depression, suicide and risk-taking behaviours.

MedlinePlus states that sleep deprivation can impair thinking, reaction time and memory, thereby increasing the risk of mistakes and accidents, and can cause irritability, depression and anxiety.

Key points

Recommended hours of sleep per day according to the CDC for the young: newborn (0 to 3 months) 14 to 17 hours; infant (4 to 12 months) 12 to 16 hours including naps; toddler (1 to 2 years) 11 to 14 hours including naps; preschool (3 to 5 years) 10 to 13 hours including naps; school age (6 to 12 years) 9 to 12 hours.

According to the CDC for teenagers and adults: teenager (13 to 17 years) 8 to 10 hours; adult (18 to 60 years) 7 hours or more; adult (61 to 64 years) 7 to 9 hours; 65 years and over 7 to 8 hours.

NHLBI states that experts recommend adults sleep between 7 and 9 hours a night, and that adults who sleep less than 7 hours may have more health problems than those who sleep 7 hours or more. Sleeping more than 9 hours is not necessarily harmful, and may be beneficial for young adults, people recovering from sleep deprivation, and the ill.

NHLBI states that the sleep patterns of newborns under 4 months vary widely, and gives 8 to 10 hours a day (including naps) for ages 13 to 18. MedlinePlus gives adults (18 years and over) 7 to 9 hours, and the NHS gives approximate ranges: adults 7 to 9 hours, children 9 to 13 hours, and babies and toddlers 12 to 17 hours.

The CDC states that signs of poor sleep quality include: difficulty falling asleep, waking frequently during the night, and feeling sleepy or tired even after getting enough sleep.

NHLBI reports that research it funded found that adults who regularly sleep 7 to 8 hours a night have a lower risk of obesity and high blood pressure.

According to NHLBI: after several nights of lost sleep, even just 1 to 2 hours a night, your performance is affected as though you had not slept for a day or two. It estimates that drowsy driving is a factor in about 100,000 car crashes a year, resulting in about 1,500 deaths.

US figures given by NHLBI: about 1 in 3 adults in the United States reported not getting enough rest or sleep every day, about 40% of adults unintentionally fall asleep during the day at least once a month, and an estimated 50 to 70 million Americans have chronic sleep disorders.

How to put it into practice

Keep a schedule: go to sleep and wake up at the same time every day (CDC, MedlinePlus and NHLBI), and keep the difference between workdays and weekends to no more than about an hour (NHLBI). NHLBI advises giving yourself enough time to sleep.

Prepare the bedroom: quiet, comfortable and cool (CDC), dark (MedlinePlus and NHLBI), and a dim night light is fine if needed (NHLBI). The NHS suggests blackout curtains, an eye mask or earplugs if needed, and a comfortable bed, pillows and covers.

Reduce screens and bright light: the CDC advises turning off electronic devices at least 30 minutes before bedtime, and NHLBI advises making the last hour before bed a quiet time with no strenuous exercise or bright light such as television or computer light. The NHS notes that the blue light from devices keeps you awake.

Watch out for stimulants: the CDC advises avoiding caffeine in the afternoon and evening, NHLBI states that the effect of caffeine can last up to 8 hours, and the NHS advises not smoking or drinking tea or coffee within 6 hours of bedtime. MedlinePlus and NHLBI advise avoiding nicotine; see quitting smoking.

Food and drink: avoid large meals before bed (CDC), a small light snack is fine (NHLBI), and MedlinePlus advises avoiding large meals and lots of drinks late at night.

Daytime activity, diet and light: do regular physical activity and follow a healthy diet (CDC), but not right before bed (MedlinePlus); the NHS advises not exercising within 4 hours of bedtime. MedlinePlus advises exposure to sunlight during the day, and NHLBI spending time outdoors every day if possible.

Naps: NHLBI states that an adult's nap should not be longer than 20 minutes, and that anyone who has trouble sleeping at night should cut down on naps or take them earlier in the afternoon. MedlinePlus advises not napping after 3 p.m.

Wind-down routine: a warm bath or relaxation techniques before bed (NHLBI), or reading or calm music (MedlinePlus), and the NHS advises relaxing for at least an hour before bed, going to bed only when feeling sleepy, and not sleeping late in the morning after a bad night.

If you cannot fall asleep within 20 minutes, get up and do something relaxing (MedlinePlus).

Sleep diary: your care provider may ask you to record bedtimes, night-time and morning wake times, naps, exercise, caffeinated drinks and medicines (CDC), and NHLBI suggests recording them for a few weeks along with how alert you feel.

Special groups

Children: NHLBI advises a consistent bedtime and a bedtime routine for the child, and not using their bedroom for punishment. It states that naps are normal for preschool children and support growth and development, and that sleep experts consider naps appropriate for children under 7.

According to NHLBI, sleep deficiency in children may show up as hyperactivity, difficulty paying attention, poor behaviour and a decline in school performance. It states that a child with sleep apnoea may be hyperactive and may wet the bed, and asthma symptoms may worsen. Discuss it with your child's doctor.

Teenagers: MedlinePlus states that the biological clock shifts during puberty so that teenagers tend to fall asleep and wake later, which may conflict with an early school start. NHLBI explains that teenagers go to sleep later at night than younger children and adults, because their peak of the hormone melatonin is delayed.

Older adults: MedlinePlus says there is no evidence that adults need less sleep as they age, but older people often sleep less or spend less time in deep sleep and wake more easily. Its medical encyclopaedia adds that older people's sleep is lighter and more broken, and that a healthy 70-year-old may wake several times at night without this being due to illness. See healthy ageing.

MedlinePlus states that disturbed sleep in older adults may be linked to Alzheimer's disease, heart failure, certain medicines, depression, arthritis pain, needing to urinate at night, inactivity, caffeine and nicotine, and that before prescribing any sleep medicine a care provider should assess the risk of daytime sleepiness and effects on thinking and falls. NHLBI states that sleep deficiency in older adults may be linked to more falls and bone fractures.

Shift workers: MedlinePlus and NHLBI suggest taking naps and increasing the time available for sleep, keeping lighting bright at work, minimising shift changes so the body can adapt, limiting caffeine to the first part of the shift, and blocking light and noise when sleeping during the day (blackout curtains or earplugs). Those who still cannot sleep during the day or find it hard to adapt should talk to their doctor, according to NHLBI.

Pregnancy: NHLBI states that research it funded found that untreated sleep disorders raise the risk of heart problems and problems during pregnancy, including high blood pressure and diabetes. What suits a pregnant woman is decided by her doctor.

Risks and cautions

Drowsiness and driving: NHLBI states that studies show sleep deficiency impairs driving ability as much as driving under the influence of alcohol, or more, and that brief "microsleeps" can happen without the person noticing. The NHS advises not driving when feeling drowsy.

Sleep disorders: the CDC says some people have health conditions that stop them getting enough good sleep no matter how hard they try, called sleep disorders, among the most common of which are insomnia, restless legs syndrome, narcolepsy and sleep apnoea.

Sleep apnoea: NHLBI lists among its symptoms breathing that stops and starts during sleep, loud and frequent snoring, gasping for air, and daytime sleepiness and fatigue, and you may not know you have these symptoms until someone else tells you. It states that untreated sleep disorders raise the risk of heart problems.

Insomnia: the NHS defines it as regular problems with sleep, such as difficulty falling asleep, waking several times, waking early and being unable to get back to sleep, or feeling tired after waking. It is called long-term if it lasts 3 months or more. Common causes include stress, anxiety, depression, noise, alcohol, caffeine, nicotine, jet lag and shift work, and many medicines may cause it. The NHS states that it usually improves with changes to sleep habits.

Sleep medicines: the NHS states that sleeping pills are rarely prescribed today because of serious side effects and the risk of dependence, that pharmacy sleep products do not treat insomnia and may cause drowsiness that affects driving, and advises seeing a doctor before taking anything for sleep problems. MedlinePlus states that the US Food and Drug Administration (FDA) imposed stronger warnings on some sleep medicines, covering severe allergic reactions and dangerous behaviours during sleep such as sleep-driving. Any sleep medicine, whether starting or changing, is decided by the doctor.

When to see a doctor: the CDC advises seeing a care provider if you have regular sleep problems or notice signs of the common sleep disorders, and MedlinePlus advises seeing one if difficulty sleeping persists. The NHS advises seeing a primary care doctor if changing sleep habits has not helped, difficulty sleeping has lasted for months, or insomnia is making daily life hard to cope with. NHLBI states that doctors may not notice sleep problems at routine visits, so tell your doctor if you suspect them, such as daytime sleepiness, waking unrefreshed, or difficulty adjusting to shift work.

What the doctor may do: the CDC and NHLBI state that a care provider may ask for a sleep diary or a sleep study (polysomnography), which are painless tests that measure the quality of your sleep. The NHS states that the doctor tries to identify the cause, may suggest cognitive behavioural therapy for insomnia, and may refer you to a specialist sleep clinic if there is another disorder such as sleep apnoea.

Limits of this information

The figures here come from US bodies (CDC, NHLBI and MedlinePlus) and a British one (NHS), and they differ slightly from one another; for example, the CDC defines the teenage group as 13 to 17 years whereas NHLBI and MedlinePlus define it as 13 to 18 years, and the CDC gives newborns from 0 to 3 months 14 to 17 hours whereas NHLBI says their sleep patterns vary widely. Each person's need for sleep differs, and what suits you is decided by your doctor according to your age and condition.

The prevalence and accident figures cited relate to the United States as presented by NHLBI, and may differ in other countries.

The link between too little sleep and disease as presented by the source pages is mostly an association and an increase in risk, and does not mean that sleep alone causes or prevents disease.

The source pages did not mention emergency signs specific to sleep, and advise seeing a care provider; so the warning signs here are signs for booking an appointment with the doctor, except for not driving when drowsy. This page does not cover the details of treating sleep disorders such as sleep apnoea.

The National Institute on Aging (NIA) pages on sleep in older adults could not be read, so the MedlinePlus medical encyclopaedia was used for this group.

Common questions