Why Sleep Matters

What happens

• Two systems time your sleep: a body clock set by light, and sleep pressure from adenosine that builds while you're awake. Caffeine blocks adenosine.
• Sleep runs in cycles of about 90 minutes, four to six a night. Deep sleep supports repair and memory; REM sleep is when most vivid dreams happen.
• Most adults need 7 to 9 hours a night; adults 65 and older, 7 to 8 hours.
• Regular short sleep is linked to high blood pressure, type 2 diabetes, weight gain, heart disease and depression, and drowsy driving is dangerous.
• Loud snoring with gasping or pauses in breathing can mean sleep apnea, which is treatable. For ongoing insomnia, CBT-I is the recommended first treatment.

What you can do

• Go to bed and get up at about the same time every day, weekends included.
• Get some daylight in the morning.
• Avoid caffeine in the afternoon and evening, and don't use alcohol as a sleep aid.
• Keep your bedroom cool, dark and quiet.
• Wind down before bed with lights low and screens put away.
• If you can't fall asleep after about 20 minutes, get up and do something calm in dim light, then go back to bed when you feel sleepy.

Common questions

How many hours of sleep do adults need?

Canadian guidelines recommend 7 to 9 hours a night for adults aged 18 to 64, and 7 to 8 hours for adults 65 and older, with consistent bed and wake-up times. The American Academy of Sleep Medicine recommends 7 or more hours for adults.

Does a drink before bed help you sleep?

Not really. Alcohol can make you fall asleep faster, but it breaks up sleep later in the night and reduces REM sleep, so you tend to wake up less rested.

What is the best treatment for insomnia?

For long-lasting (chronic) insomnia, guidelines recommend cognitive behavioural therapy for insomnia (CBT-I) as the first treatment. It is a short program that changes sleep schedules and habits and eases worries about sleep, and its benefits tend to last longer than sleeping pills. Ask your health care provider about options.

Transcript

You'll spend about a third of your life asleep. But while you rest, your body and brain are hard at work.

Sleep repairs the body, sorts the day's memories, and resets your mood. Let's look at what happens while you rest, and why sleep matters so much.

Two systems decide when you feel sleepy. The first is your body clock: a tiny cluster of cells deep in the brain that keeps a rhythm of about twenty-four hours.

The clock sets itself mainly by light. Morning light tells it the day has begun. As darkness falls, the brain releases a hormone called melatonin, a signal that night is coming.

The second system is sleep pressure. From the moment you wake up, a chemical called adenosine slowly builds in your brain. The longer you're awake, the stronger the pull to sleep.

Caffeine works by blocking adenosine. You feel more alert, but the pressure is still building. And caffeine can linger for hours, so an afternoon coffee can keep you up at night.

At night, when the clock and the pressure line up, you drift off. Sleep clears the adenosine away, so you wake up reset.

Sleep isn't one long, even state. It comes in cycles of about ninety minutes, and most nights you go through four to six of them.

Each cycle starts with light sleep. Then comes deep sleep, when brain waves become slow and large. This is when the body releases growth hormone and does much of its repair work.

Deep sleep also helps lock in memories, moving what you learned during the day into longer-term storage.

Then comes REM sleep, named for the rapid eye movements. The brain becomes very active, and this is when most vivid dreams happen. Most of your muscles go limp, so you don't act out your dreams.

REM sleep seems to help us process emotions. And REM periods grow longer toward morning, so a short night cuts into it.

Sleep touches almost every part of your health. It steadies your mood, helps your immune system fight infections, and keeps the hormones that control hunger in balance.

In deeper sleep, your heart rate and blood pressure fall, giving your heart and blood vessels a nightly rest.

And studies, mostly in animals, suggest the brain may clear away waste while you sleep. Scientists are still working out how this happens in people.

So how much sleep do adults need? Canadian guidelines recommend seven to nine hours a night for most adults, and seven to eight from age sixty-five.

Yet about one in three adults regularly gets less than seven hours. In the short term, that means slower reactions and a shorter temper. Drowsy driving can be as dangerous as drunk driving.

Over years, regularly sleeping too little is linked to higher risks of high blood pressure, type 2 diabetes, weight gain, heart disease and depression.

Some people spend long enough in bed, but still sleep poorly. Loud snoring, gasping or pauses in breathing, and daytime sleepiness can be signs of sleep apnea, where the airway keeps closing during sleep.

Sleep apnea is common, and it's treatable. If this sounds like you, or someone you sleep beside, talk to your health care provider.

Trouble falling or staying asleep, night after night, may be insomnia. The first treatment experts recommend isn't a pill. It's a short program called CBT-I: cognitive behavioural therapy for insomnia. Its benefits tend to outlast sleeping pills.

So what can you do? Keep a steady schedule, going to bed and getting up at about the same time every day, even on weekends. And get some daylight in the morning.

Avoid caffeine in the afternoon and evening. Keep your bedroom cool, dark and quiet. And give yourself time to wind down, with the lights low and screens put away.

If you can't fall asleep after about twenty minutes, get up and do something calm in dim light. Go back to bed when you feel sleepy. That teaches your brain that bed is for sleeping.

One common myth is that a nightcap helps you sleep. Alcohol may help you drift off, but it breaks up sleep later in the night and cuts into REM, so you wake up less rested.

So, to recap. Your body clock and sleep pressure set the timing. Deep and REM sleep repair the body and sort memories. Most adults need seven to nine hours. And steady habits help.

Now you know what happens while you rest. Look after your sleep, and it will look after you.

Sources

1. Canadian 24-Hour Movement Guidelines for Adults (CSEP, 2020)
2. NHLBI — What Makes You Sleep? (body clock and sleep drive)
3. NHLBI — Stages of Sleep
4. NHLBI — Health Effects of Sleep Deprivation
5. CDC — About Sleep
6. Watson NF et al. Recommended amount of sleep for a healthy adult (AASM/SRS). J Clin Sleep Med 2015
7. Qaseem A et al. Management of chronic insomnia disorder in adults (ACP guideline). Ann Intern Med 2016
8. Ebrahim IO et al. Alcohol and sleep I: effects on normal sleep. Alcohol Clin Exp Res 2013