Why sleep matters for health
Sleep is a biological need, not a luxury. While people sleep, the body and brain carry out a range of maintenance tasks, and researchers have linked long-term short or poor sleep with higher risks of several health problems, including difficulty regulating mood, weight gain, and changes in blood pressure and blood sugar control. These are associations from large studies, and in many cases researchers are still working out how much is cause and how much is effect. This article offers general information, not medical advice.
The stages of sleep, briefly
A night of sleep is not one uniform state. It is made of stages that repeat in cycles.
- Light sleep (often called N1 and N2). The transition from waking, followed by a stage in which heart rate and body temperature drift down. Most of the night is spent here.
- Deep sleep (N3, or slow-wave sleep). The hardest stage to wake from. It tends to be concentrated in the first half of the night and is associated with physical restoration.
- REM sleep. Brain activity rises, the eyes move rapidly under the lids, and most vivid dreaming occurs. The body’s voluntary muscles are largely switched off. REM periods tend to lengthen toward morning. Our piece on REM sleep dreams goes further into this stage.
A cycle through these stages typically takes roughly an hour and a half, though this varies, and most people go through several cycles a night. The fuller picture of how the stages fit together is covered in our article on sleep cycles.
How much sleep do people typically need?
Needs vary between individuals, so the numbers below are broad guidelines reflecting commonly cited recommendations rather than strict rules.
| Group | Typical range per 24 hours |
|---|---|
| Newborns | Roughly 14 to 17 hours, in short stretches |
| Infants | Roughly 12 to 16 hours, including naps |
| Toddlers | Roughly 11 to 14 hours, including naps |
| School-age children | Roughly 9 to 12 hours |
| Teenagers | Roughly 8 to 10 hours |
| Adults | Roughly 7 to 9 hours |
| Older adults | Often around 7 to 8 hours |
Older adults often find sleep lighter and more broken, which is common, but major changes are worth discussing with a doctor. Whether you are getting enough is usually judged by how you function: waking reasonably refreshed and staying alert in the daytime are better signs than a number alone.
What is sleep hygiene?
“Sleep hygiene” means everyday habits and surroundings that tend to support sleep. They are not cures for sleep disorders, but they are often the first things suggested for ordinary sleep difficulties.
Keep a regular schedule. Going to bed and getting up at similar times, including on days off, helps keep the body clock steady. Large weekend swings can feel like a mild bout of jet lag.
Get daylight. Morning and daytime light helps anchor your internal clock. Dimmer light in the evening is generally more helpful than bright light.
Watch caffeine and alcohol. Caffeine can stay in the body for many hours, so late-day coffee, tea or energy drinks may interfere with falling asleep. Alcohol may make some people drowsy but tends to disrupt sleep later in the night.
Time meals and exercise sensibly. A very heavy meal close to bedtime can be uncomfortable. Regular activity during the day is associated with better sleep for many people, though some find vigorous exercise very late in the evening stimulating.
Make the bedroom suitable. Cool, dark and quiet works for most people. Using the bed mainly for sleep, rather than for work or scrolling, helps some people associate it with rest.
Wind down. A consistent, calming routine, such as reading, gentle stretching or a warm shower, can signal that the day is ending. Some people find that deep breathing helps them relax.
Be thoughtful about screens. Bright screens and stimulating content close to bedtime may delay sleepiness for some people. Dimming devices and putting them away a while before bed is a common suggestion, though the size of the effect varies.
Do not lie awake for long. If you cannot sleep after what feels like a good while, many sleep specialists suggest getting up, doing something quiet in low light, and returning when sleepy, so that the bed does not become linked with frustration.
Be careful with naps. Short early-afternoon naps suit some people, whereas long or late ones can make nighttime sleep harder.
When to seek help
Good habits help ordinary sleeplessness, but they will not fix every problem. Consider talking with a doctor if you:
- have trouble sleeping most nights for several weeks
- snore loudly, gasp or stop breathing during sleep, or wake with morning headaches
- feel very sleepy during the day despite spending enough time in bed
- have uncomfortable sensations in your legs that make it hard to settle
- rely on sleep aids regularly
Conditions such as insomnia and sleep apnea are common and treatable, and a professional can recommend options suited to your situation. Avoid starting supplements or medications without advice.
A realistic view
Perfect sleep every night is not a realistic goal, and worrying about sleep can itself make it worse. A broadly regular schedule, a sensible evening routine and attention to daytime habits tend to be a reasonable foundation, and occasional bad nights are a normal part of life.