What Is Sleep Health and Why Does It Matter?

Let's start with a definition. Sleep researcher Daniel Buysse proposed one in 2014, quoted in later research. Sleep health is "a multidimensional pattern of sleep-wakefulness, adapted to individual, social, and environmental demands, that promotes physical and mental well-being."^[1][2] In plain English: sleep that works for your real life and keeps you well. It isn't a diagnosis, and it isn't one number.

The American Academy of Sleep Medicine (AASM) names the ingredients: in addition to adequate duration, healthy sleep requires good quality, appropriate timing, regularity and the absence of sleep disorders.^[3] Buysse and colleagues' model also counts alertness, which means feeling awake through the day.^[1][4] Quality means sleep that is mostly unbroken and leaves you feeling you slept well. In my coaching, I also look at how your night is built from light, deep and REM sleep.

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Here's the thing: it isn't just how many hours of sleep you get that matters. It's when, how regularly, and the architecture of the night.

Let's start with the number. Adults aged 18 to 60 are recommended to sleep at least 7 hours a night.^[5] A National Sleep Foundation expert panel set the range at 7 to 9 hours for adults, and 7 to 8 for older adults.^[6] A Statistics Canada study used the same ranges.^[7]

The panel adds that needs vary from person to person.^[6]

Time in bed isn't the same as time asleep. My guidance is an eight-hour sleep window, to get at least seven hours of actual sleep. Build the window. Protect it with what you do during the day, and at night when you can't sleep. Do those two things, and your sleep accountant will balance the books. Your sleep accountant is what I call the process that keeps track of the sleep your body needs. Build the window, and let it fill.

The AASM calls sleep a biological necessity.^[3] Here's some of what research found:

• Short sleep, more colds. In 164 healthy adults exposed to a cold virus, those who had slept under 5 hours, or 5 to 6 hours, had about four times the odds of developing a cold compared with those sleeping over 7 hours. The margins of error were wide.^[9]
• Short sleep, more hunger. In a lab study of 12 young men, two days of restricted sleep, compared with two days of extended sleep, were linked to an 18% drop in the hormone leptin and a 28% rise in the hunger hormone ghrelin. Hunger rose 24%.^[10]
• Heart health. The American Heart Association added sleep health to its "Life's Essential 8" checklist, alongside diet, physical activity and blood pressure.^[11]
• Long-term risk. A meta-analysis of 16 studies linked short sleep to a 12% higher risk of death, and long sleep to a 30% higher risk. These are links, not proof of cause.^[12]

In a small lab study, six nights of four hours in bed raised young men's evening cortisol and lowered glucose tolerance. The effects were "similar to those seen in normal ageing."^[13] I call chronic sleep debt a hyper-effective ager: in my teaching, it accelerates aging. Here's the good news: sleep health is something you can build.

Here's how I explain it. Wakefulness is actually toxic. Our brain is like an engine, and it produces exhaust. Sleep is how we wash it away. The science of how the brain clears waste during sleep is early and debated. One mouse study linked natural sleep to a 60% increase in the space between brain cells and faster clearing of waste.^[14] A 2024 mouse study found that brain clearance was reduced, not increased, during sleep and anesthesia.^[15] In 20 healthy adults, one night without sleep raised β-amyloid in two brain regions.^[16]

In a meta-analysis of 21 studies, non-depressed people with insomnia had about twice the risk of later depression.^[17] And a meta-analysis of 65 randomized trials found that improving sleep led to better mental health, including less depression, anxiety and stress.^[18]

Picture the last time you were short on sleep and snapped at someone you love. I teach it with two pedals. Reason is the brake. Emotional reactivity is the gas pedal. Short on sleep, the brake weakens and we become all gas pedal, like a tired toddler. We think that no longer applies to us as adults. It does. When we're sleep deprived, we aren't who we think we are.

In my 2019 keynote I said: "I do not envision a way that we could properly address mental health without also addressing sleep issues." If you are struggling, talk to your physician.

In a well-known experiment, healthy adults limited to six hours or less in bed a night for two weeks showed deficits equivalent to up to two nights of total sleep deprivation. Their sleepiness ratings suggest they were largely unaware of it.^[19]

After 17 to 19 hours without sleep, performance on some tests was equivalent to or worse than at a blood alcohol level of 0.05%.^[20] After about 24 hours, a coordination task matched roughly 0.10%.^[21]

I hear it all the time: "Glenn, I can function really, really well on four to five hours sleep." I'm sorry. You may feel like you're great, but you aren't your best self when you're sleep deprived.

I picture stress as rocks in a backpack. Every stressful day adds a rock. At first you can carry it. Then it gets heavier. Without enough sleep, REM sleep especially, it keeps getting heavier.

Do your sleep times change on weekends? Researchers tracked the sleep of 60,977 UK adults with accelerometers. Higher sleep regularity, the day-to-day consistency of sleep and wake times, was associated with a 20% to 48% lower risk of dying from any cause over about six years, comparing the four most regular groups with the least regular. Regularity predicted death risk better than sleep duration did.^[22]

This was observational (average age 62.8), so it can't prove that regular sleep makes people live longer.^[22]

I tell people: "If you change your sleep window during the week for workdays versus weekends, you're a shift worker." Your body clock, the part of you that runs on a roughly 24-hour cycle, doesn't know a Monday from a Sunday.

We all know what we need to do: eat right, exercise, get plenty of sleep. Here's what most people don't realize. It's not just what you do that matters, it's also when you do it. I'd argue it matters more. Timing is everything. In my teaching, circadian rhythms are the secret to sleep health. For the science of the body clock, read our guide to circadian rhythms.

• United States. In 2014, 65.2% of 444,306 adults surveyed reported sleeping at least 7 hours, so more than a third did not.^[5]
• Canada. About a third of adults slept fewer hours than recommended (self-reported).^[7] Nighttime insomnia symptoms rose 42% between 2007 and 2015, from 16.8% to 23.8%. Those are symptoms, not diagnoses.^[8]

The costs add up:

• The economy. RAND estimated that insufficient sleep costs the US economy up to US$411 billion a year (2.28% of GDP, 2015 dollars) and Canada up to about C$27 billion (1.35% of GDP).^[23]
• For companies. One survey-based study estimated fatigue-related lost productivity at about US$1,967 per employee per year (2010 study).^[24]

Sleep is the very first thing we sacrifice to meet the needs of work, family and social life. That's the bad news. The good news: normal isn't inevitable. If the goal is healthspan, not just longevity but quality of life into our later years, I'd argue we must protect our sleep. I like to think in terms of what I call sleep health status: not just today, but across your lifespan.

If you lead a team, read how sleep affects productivity at work.

Can sleep be improved? In a randomized trial, 80 adults aged 21 to 40 with overweight usually slept under 6.5 hours. One individualized counselling session extended their sleep by about 1.2 hours a night over two weeks compared with a control group. Their energy intake fell by about 270 kcal a day.^[26] It was built around each person's own life. In my experience, one-size-fits-all approaches lack impact, because we're all individuals. You may know the ingredients as sleep hygiene tips. Timing and fit to your life are what make them work; see our sleep hygiene guide.

If you snore loudly, wake up gasping or choking, stay very sleepy in the day despite enough time in bed, or have had insomnia for months, talk to your physician. A physician can assess and diagnose a sleep disorder. Habitually sleeping far outside the normal range can also be a sign of a health problem.^[6]

I don't recommend melatonin or sleep medications as a fix. If you're using them, talk to your physician before changing anything.

Not sure where you stand? The Free Sleep Assessment uses two widely used, validated questionnaires and gives you a sleep score and a sleep apnea risk score. It's a screen, not a diagnosis.