Sleep and Brain Health: What Research Suggests and What Helps

Sleep and brain health are clearly connected, but how they are connected is still being worked out. Some studies link short sleep with a higher risk of dementia. Dementia, in turn, often disrupts sleep. This page explains what the research does and does not show, gives practical sleep habits, and covers sleep problems that are common in dementia. It does not give advice about sleep medicines; that conversation belongs with a doctor.

Is poor sleep linked with dementia?

Some long-term studies link short sleep with a higher risk of dementia, but the evidence is not settled.

• A 25-year UK study. Researchers followed about 8,000 adults in the Whitehall II study. People who slept six hours or less at age 50 or 60 had a higher risk of dementia later than those who slept seven hours. People who slept six hours or less at 50, 60 and 70 had about a 30% higher risk than those who regularly slept seven hours. This was an observational study, so it shows a link, not a cause.
• The Lancet Commission’s view. The 2024 Lancet Commission did not add sleep to its list of 14 modifiable risk factors. It judged the evidence not consistent enough. One reason is “reverse causation”: brain changes from dementia begin years before diagnosis and can disturb sleep. In one large study, a link between long sleep and dementia disappeared once the first five years of follow-up were set aside.

So a short night now and then is not a reason to worry. Regular, good-quality sleep is worth aiming for because it helps mood, alertness and safety today.

What is the “brain-clearing” sleep research?

You may have read that sleep “cleans” the brain. That idea comes from real research, but it is early.

• In mice. A 2013 study described by the NIH found that the space between brain cells grew by about 60% when mice slept. Fluid flowed through the brain more easily, through what researchers call the glymphatic system. Beta-amyloid, a protein linked with Alzheimer’s, cleared faster from the brains of sleeping mice.
• In people. A small 2018 study scanned 20 healthy adults aged 22 to 72 after a normal night and after a night with no sleep. After the sleepless night, a brain scan signal for beta-amyloid rose by about 5% in an area including the hippocampus, a region important for memory. The authors called this preliminary evidence. They did not know whether the change goes away after rest, or whether it reflects slower clearing or more amyloid being made.
• It works both ways. The Lancet Commission notes that amyloid build-up can itself disturb sleep in older adults.

These findings help explain why researchers are interested in sleep. They do not show that better sleep prevents Alzheimer’s.

What sleep habits may help?

Older adults need about 7 to 9 hours of sleep a night, the same as other adults, according to the National Institute on Aging (NIA). Its suggestions include:

• Keep a regular schedule. Go to bed and get up at the same time each day, even on weekends.
• Build a wind-down routine. Read, listen to soothing music or take a warm bath before bed.
• Make the bedroom comfortable, not too hot or too cold.
• Limit caffeine late in the day. Coffee, tea, soda and chocolate can keep you awake.
• Avoid alcohol, even small amounts, the NIA advises.
• Avoid large meals within two to three hours of bedtime, and large drinks late in the day.
• Exercise regularly, but not within 3 hours of bedtime. See our exercise guide.
• Keep screens out of the bedroom. The NIA suggests not watching TV or using a computer, phone or tablet there.
• Avoid late-afternoon or evening naps if you can.

Sleep problems in dementia

Changes in sleep are common in dementia. The NIA lists sleeping a lot or too little, waking many times at night, and napping a lot during the day. It also describes sundowning: restlessness, agitation or confusion that starts or gets worse as daylight fades.

Caregiver tips from the NIA include:

1. Get daylight and movement early. Go outside or sit by a window during the day, and help the person be active each day. Bright light may help reset the body clock.
2. Plan energetic activities for the morning. Try bathing in the morning or having the largest meal at midday.
3. Keep naps short and early. Limit dozing late in the day.
4. Make the evening calm. Lower the lights, reduce noise and play soothing music if the person enjoys it. Our guide to late-day restlessness has more ideas.
5. Keep a steady bedtime routine. Reading aloud at the same time each night is one NIA example. A steady daily routine helps too.
6. Limit caffeine and alcohol.
7. Use nightlights in the bedroom, hall and bathroom.

For nighttime waking, the NIA’s home safety tips include nightlights or automatic light sensors, grab bars in the bathroom, brightly colored tape on the edges of steps, and medicines stored in a locked place.

A short, quiet activity in the evening can help you both settle. Try a slow Calm Breathing pause or a few relaxed Conversation Cards. Skip anything stimulating close to bed, and stop whenever the person has had enough.

Broken sleep wears caregivers down too. Our caregiver self-care guide covers ways to get rest and help.

What about sleep apnea?

Sleep apnea causes short pauses in breathing during sleep, often many times a night. The NIA says that if it is not treated, it can lead to problems such as high blood pressure, stroke or memory loss. Signs include loud snoring and feeling sleepy during the day, and many people do not know they have it. The Lancet Commission describes a review of 11 studies in which people with sleep apnea had about a 43% higher risk of dementia. Few of those studies accounted for weight, though, so the link is uncertain.

Sleep apnea can be diagnosed and treated. The NIA notes that a CPAP machine almost always helps. If you or the person you care for snores loudly, stops breathing during sleep, or is very sleepy during the day, tell a doctor.

A note about sleep medicines

We do not give advice about sleep medicines or supplements. The NIA notes that sleep medicines may help for a short time but are not a cure for insomnia. It also notes that some medicines given to help people with Alzheimer’s sleep can raise the risk of dizziness, falls and confusion. Do not start, stop or change any sleep medicine, including over-the-counter sleep aids, without talking to a doctor or pharmacist.

Talk with a doctor

See a doctor if you or the person you care for is always tired, has trouble sleeping most nights, snores loudly, or has pauses in breathing at night. If sleep problems in dementia keep going, the NIA advises seeking medical advice. A check-up can find causes such as pain, another sleep disorder, an illness or a medicine side effect. Sudden confusion, or a sudden change in sleep alongside confusion, needs urgent care. Read when to see a doctor.

This page is general information, not medical advice. See our medical disclaimer.