Sleep

Why sleep matters#

Short or irregular sleep shows up in almost every organ system. In 2022 the American Heart Association added sleep to its core measures of heart health, alongside blood pressure, cholesterol, and smoking, with seven to nine hours as the adult target.

• Metabolism. In a 2022 trial of 80 short sleepers with overweight, sleep counseling added about 1.2 hours a night and cut intake by about 270 kcal a day, with no diet advice.
• Mental health. Insomnia roughly doubled the risk of later depression in a meta-analysis of 21 long-term studies.
• Dementia. In the British Whitehall II cohort of 7,959 people followed for 25 years, persistent sleep of six hours or less in midlife and beyond carried about 30% higher dementia risk than seven hours. It is observational, and early brain disease also disturbs sleep. See brain health.
• Safety. Drowsy drivers crash far more often (see the numbers below and driving).

Regularity may matter as much as duration. A 2023 study tracked the sleep of 60,977 UK Biobank participants with wrist sensors. Compared with the least regular fifth, the more regular groups had a 20% to 48% lower risk of death over about six years, and regularity predicted mortality better than total sleep time. It is observational, so some irregular sleepers were probably already unwell.

How much you need#

Optimal: 7 to 9 hours of actual sleep a night, and for most adults about 7 to 8. That is the range the American Heart Association scores as ideal in Life's Essential 8, and it is where mortality is lowest: in a meta-analysis of 1.38 million people, short sleep was linked to 12% and long sleep to 30% higher mortality Moderate. Long sleep probably reflects illness more than it causes harm, so do not force extra hours in bed, which can feed insomnia. Needing much more than nine hours without a reason is worth mentioning to a doctor.

Guideline minimum: the American Academy of Sleep Medicine and the Sleep Research Society recommend seven or more hours a night for adults 18 to 60, with more than nine appropriate for young adults, people recovering from sleep debt, and people who are ill (AASM).

Those numbers are for actual sleep, not time in bed. Most people spend some of the night awake, so 7–8 hours of sleep usually takes 8–9 hours in bed.

Keep the timing steady too. In 1,992 adults who wore wrist sensors for a week, those whose bedtime varied by more than 90 minutes from night to night had about twice the risk of heart attacks, strokes, and other cardiovascular events over five years as those who varied by 30 minutes or less, after adjusting for how long they slept Moderate. Optimal: bedtime and wake time within about 30 minutes every day, weekends included. No guideline sets a regularity target.

Signs you are short: you need an alarm every day, sleep much longer on free days, or nod off as a passenger. To know your real numbers, wear a tracker or keep a sleep diary for two weeks once or twice a year and look at average sleep time and how much your bedtime moves.

Your body clock in plain language#

Two systems decide when you feel sleepy.

When the two line up, you are sleepy at night and alert in the morning. Jet lag, shift work, late screens, and weekend sleep-ins pull them apart.

Your chronotype is where your clock naturally sits, from early "larks" to late "owls." It is partly genetic: a 2019 study of 697,828 people found 351 gene regions linked to being a morning person. It also changes with age. People drift later through adolescence, reach their latest timing around age 20, and then get earlier again. Light and routine can nudge your clock earlier or later, but they will not turn an owl into a lark, so pick a schedule you can keep seven days a week.

The levers that work#

Some of these habits are backed by trials; others are reasonable practice built on how the clock works.

Regularity#

Pick a wake time you can hold every day, within about 30 minutes, and work backward to a bedtime 8–9 hours earlier. After a late night, get up at about the usual time and go to bed earlier the next night rather than sleeping until noon.

Light#

A 2022 expert consensus recommends bright light during the day (at least 250 lux at eye level in its circadian measure, more than most indoor lighting provides and far less than daylight), under 10 lux in the three hours before bed, and under 1 lux while you sleep.

In practice: get outside soon after waking, longer when it is overcast. After sunset, use dim lamps instead of overhead lights and keep screens dimmer. Make the bedroom dark with blackout shades or a mask. A 2023 Cochrane review found too little good evidence that blue-light-blocking glasses improve sleep Weak; dimming the room does more.

Temperature#

Your core temperature has to drop for good sleep. Most guidance suggests a bedroom of about 65–68°F (18–20°C), but the best setting varies. A 2023 study of older adults living at home found they slept most efficiently between 68 and 77°F (20–25°C), with worse sleep as rooms got hotter. Aim for cool enough to be comfortable under a light cover, and treat heat above about 77°F (25°C) as the bigger problem.

A warm bath or shower helps by pulling heat to your skin so your core can cool. In a 2019 meta-analysis, water at about 104–108.5°F (40–42.5°C) taken one to two hours before bed, for as little as 10 minutes, shortened the time it took to fall asleep.

Wind-down and the bed#

A calm, repeated routine at the end of the evening tells your brain the day is over. Keep the bed for sleep and sex. If you are lying awake and frustrated, get up, do something quiet in dim light, and return when sleepy. That habit is "stimulus control," part of CBT-I.

Exercise timing#

Regular exercise generally improves sleep, and the old rule against evening workouts is mostly wrong. A 2019 meta-analysis of 23 studies found evening exercise did not harm sleep, except that vigorous exercise ending within an hour of bedtime could delay sleep onset. See exercise.

Caffeine, alcohol, nicotine, and food#

• Caffeine has an average half-life of about five hours, but it ranges from about 1.5 to 9.5 hours between people. In a small trial, 400 mg of caffeine taken even six hours before bed measurably disrupted sleep. An early-afternoon cutoff is a safe default. See nutrition for coffee and tea.
• Alcohol is a sedative, not a sleep aid (see the box below and alcohol).
• Nicotine is a stimulant, and overnight withdrawal can wake people who smoke or vape. See tobacco and nicotine.
• Food and fluids. Finish big meals a few hours before bed and taper fluids in the evening if reflux or bathroom trips wake you. This is common sense rather than tested rules.

Naps#

Naps are fine if they do not steal from the night. About 20 minutes, and no longer than 30, boosts alertness without the grogginess of deep sleep; take it in the early afternoon. Skip naps while treating insomnia. Needing long naps most days despite a full night in bed is worth raising with a doctor.

Insomnia and CBT-I#

Insomnia means persistent trouble falling asleep, staying asleep, or waking too early, with daytime consequences. Short bouts after stress are normal. When it lasts for months it becomes self-sustaining, as worry and time awake in bed teach the brain that bed is for being awake.

Cognitive behavioral therapy for insomnia (CBT-I) is the first-line treatment. The American College of Physicians recommends it for all adults with chronic insomnia before any medication, and the American Academy of Sleep Medicine gives multicomponent CBT-I its only strong recommendation among behavioral treatments Strong. In a 2015 meta-analysis of 20 trials, CBT-I shortened the time to fall asleep by about 19 minutes, cut time awake during the night by about 26 minutes, and the gains lasted after treatment ended. Sleep hygiene tips alone are not recommended as a treatment; they help, but they are not enough.

How to get CBT-I#

• A therapist trained in behavioral sleep medicine, usually over a handful of weekly sessions. Ask your doctor or a sleep clinic for a referral.
• Prescription digital programs. SleepioRx is an FDA-cleared app that delivers CBT-I, and some insurers and employers cover it.
• Free tools. The VA's Insomnia Coach app is built for anyone to use on their own, and its CBT-i Coach is designed to support work with a clinician.

Sleep medications#

Sleep medicines can help, but they treat symptoms rather than causes and each class has trade-offs. This is information for a conversation with your doctor, not advice to start or stop anything.

Two cautions apply broadly. The American Geriatrics Society's Beers Criteria list benzodiazepines, z-drugs, and first-generation antihistamines among medicines to avoid in most adults 65 and older, because of falls, confusion, and crashes. And never stop a benzodiazepine abruptly after regular use; taper with a prescriber.

Melatonin#

Melatonin is the hormone that signals darkness. It is better at shifting the clock than at knocking you out.

• For insomnia, it is weak. A meta-analysis of 19 trials with 1,683 people found it shortened the time to fall asleep by about 7 minutes and added about 8 minutes of sleep. The AASM suggests against it for chronic insomnia Weak.
• For jet lag, it works. A Cochrane review found melatonin taken close to the target bedtime at your destination reduced jet lag on flights crossing five or more time zones. Doses from 0.5 to 5 mg worked similarly, and more than 5 mg was no better Moderate.
• Labels are unreliable. In a 2023 analysis of US melatonin gummies, products contained 74% to 347% of the labeled dose. Keep gummies away from children.
• Long-term safety is less settled than assumed. An unreviewed 2025 conference abstract of 130,828 adults with insomnia found that people who used melatonin for a year or more had higher rates of heart failure. It cannot show cause, but it argues for targeted use rather than a nightly habit.

Magnesium and other supplements#

Magnesium is popular and low risk at normal doses, but the evidence that it improves sleep in people who are not deficient is weak Weak. The AASM suggests against valerian and tryptophan for insomnia. See supplements for quality and interactions.

Sleep apnea#

In obstructive sleep apnea (OSA), the airway repeatedly narrows or closes during sleep and the brain briefly wakes to restart breathing, usually without you knowing. Severity is measured by the apnea-hypopnea index (AHI), the number of breathing events per hour of sleep. Five or more counts as OSA, and 15 or more as moderate to severe.

It is common. A 2019 analysis estimated that 936 million adults aged 30 to 69 worldwide have at least mild OSA and 425 million have moderate to severe disease (the study was funded by ResMed, a CPAP maker). Untreated OSA is linked to high blood pressure, atrial fibrillation, stroke, heart failure, and daytime sleepiness that causes crashes (AHA 2021).

Who should get tested#

Optimal: get a home sleep apnea test if you snore regularly, even if you feel rested, or if you score three or more on STOP-Bang (below), or if you have high blood pressure (especially if it is hard to control), atrial fibrillation, heart failure, coronary disease, or a past stroke. Most apnea is missed: in a study of 4,925 working adults, 82% of men and 93% of women with moderate to severe disease had never been diagnosed. In those heart and blood vessel conditions 40% to 80% of patients have OSA, and the American Heart Association recommends screening people with resistant high blood pressure or recurrent atrial fibrillation whether or not they feel sleepy.

Retest after a weight change of about 10% or more, or if snoring or sleepiness returns: in one cohort, a 10% weight gain predicted a 32% rise in AHI and a 10% loss a 26% fall. Testing this way goes beyond the guidelines Weak; the case rests on how often apnea is missed, its links to high blood pressure, atrial fibrillation, and crashes, and the low cost and risk of a home test. Treating mild apnea without symptoms is a judgment call with your doctor, since the proven benefits of treatment are on symptoms, sleepiness, and quality of life (see the box below).

Guideline minimum: the US Preventive Services Task Force found insufficient evidence to screen adults who have no symptoms.

The STOP-Bang questionnaire is a quick way to gauge your risk: three or more "yes" answers means high risk.

Other clues include morning headaches, frequent night urination, and hard-to-control blood pressure.

Testing#

For otherwise healthy adults with signs of moderate to severe OSA, a home sleep apnea test is an accepted alternative to an overnight lab study. People with significant heart or lung disease, or a negative home test despite symptoms, should get an in-lab study. A wearable that flags "breathing disturbances" is a reason to get tested, not a diagnosis (see wearables).

Treatment#

Tirzepatide (Zepbound) is the first drug approved for OSA. In two year-long trials of 469 adults with obesity and moderate to severe OSA, it lowered the AHI by about 25 to 29 events per hour, compared with about 5 on placebo, mostly through weight loss Strong. See metabolic health for how these drugs work and their side effects.

For hypoglossal nerve stimulation, a 2014 trial of 126 people who could not tolerate CPAP found the median AHI fell 68% at a year.

Other sleep problems#

Restless legs#

Restless legs syndrome is an uncomfortable urge to move the legs that is worse at rest and in the evening. The AASM's current guideline (2025) recommends checking iron levels in everyone with significant symptoms and considering iron if ferritin is 75 ng/mL or lower or transferrin saturation is under 20%. It now favors gabapentin-type drugs and advises against routine use of the dopamine drugs (pramipexole, ropinirole, rotigotine) that were once first-line, because over time they can worsen symptoms (augmentation). Do not start iron without testing.

Jet lag#

Your clock adapts to a new time zone gradually, and for most people flying east is harder, because it means falling asleep earlier than your body wants. To adapt faster:

• Before a big trip, shift your sleep gradually toward the destination schedule if you can.
• On arrival, get daylight in the local morning after flying east and in the local late afternoon after flying west, and keep evenings dim.
• Consider melatonin at the local bedtime for the first few nights, at the dose used in trials (0.5 to 5 mg). Taken at the wrong time of day, it can delay adaptation.
• Avoid alcohol on the flight and limit caffeine to the local morning.

Shift work#

Night shifts force you to sleep when your clock says wake. The International Agency for Research on Cancer classifies night shift work as probably carcinogenic (Group 2A). If you work nights:

• Protect a consistent main sleep block with blackout curtains, earplugs, and a silenced phone.
• Use bright light early in the shift and sunglasses on the commute home.
• Nap or get a ride if you are fighting sleep after a shift.

Mouth taping, trackers, and gadgets#

Mouth taping#

Mouth taping spread on social media as a fix for snoring and mouth breathing. A 2025 systematic review found only 10 small studies with 213 people. Two showed modest improvements, most showed none, and the authors warned of potentially serious harm, including suffocation when the nose is blocked. A 2026 meta-analysis found only two small taping studies to review, while confirming that nasal obstruction worsens apnea Weak.

Sleep trackers#

Rings and watches are reasonably good at total sleep and timing and weaker at sleep stages (see wearables). Use them to check your average sleep time and regularity (two weeks once or twice a year is enough) and to spot patterns, such as what a late dinner or a drink does to your night. Sleep researchers coined the term orthosomnia for people whose pursuit of a perfect sleep score makes their sleep worse. If checking your score makes you anxious, take the device off for a few weeks.

The bedroom#

Dark, quiet, cool, and used only for sleep covers most of it.

Temperature-controlled bed systems pump water or air through a mattress cover. The Eight Sleep Pod 6 costs about $2,900 for a queen, plus about $300 a year for its software plan, and the Chilipad from Sleepme costs up to about $1,600 with no subscription (2026 prices). They can help people who run hot or share a bed with someone who does not, but no independent trials show health benefits. A fan, lighter bedding, and a lower thermostat do much the same for far less.

Action plan#