How much sleep do adults really need?

Sleep is the habit my patients are most willing to trade away. Work runs late, kids wake up, the phone comes to bed. I understand it, because I've lived it through residency, Army training and a deployment. But sleep is not wasted time. It's when your body and brain do their repair work, and the research on how much we need is clearer than most people think.

The number: 7 or more hours

In 2015, the American Academy of Sleep Medicine and the Sleep Research Society brought together a panel of sleep experts to review the research and agree on a number. Their recommendation: adults should sleep 7 or more hours a night, on a regular basis, for the best health.

That means 7 hours of actual sleep, not 7 hours in bed. Almost no one sleeps every minute they spend in bed, which is why my sleep prescription asks you to allow 8 hours in bed.

What short sleep is linked to

The same panel found that regularly sleeping less than 7 hours is associated with:

• Weight gain and obesity
• Diabetes
• High blood pressure
• Heart disease and stroke
• Depression
• A higher risk of death

They also linked short sleep to weaker immune function, more pain, poorer performance, more mistakes and a higher risk of accidents. Much of this research is observational, so it shows a link rather than proof that short sleep causes each problem. But the pattern shows up across so many outcomes that I treat sleep as seriously as diet and exercise.

Can you sleep too much?

For young adults, people catching up after a stretch of poor sleep, and people who are ill, more than 9 hours can be normal and appropriate. For everyone else, the panel said it's uncertain whether sleeping more than 9 hours carries any health risk.

What I watch for is a change. If you used to feel rested on 7 or 8 hours and now need 10 and still wake up tired, that's worth a visit. Sleep apnea, thyroid problems, depression, medication side effects and other conditions can all show up this way.

How to tell if you're short on sleep

A sleep tracker can help, but your own body is a good guide. You're probably not getting enough if you:

• Need an alarm every morning and hit snooze more than once
• Sleep 2 or more hours longer on days off
• Get drowsy while reading, watching TV or in meetings
• Rely on caffeine to get through the afternoon
• Have ever felt drowsy behind the wheel

Drowsy driving is the one I take most seriously. If you've nodded off while driving, even for a second, please tell your doctor.

When habits aren't enough

For most people, a steady schedule and a cool, dark, quiet bedroom go a long way. Those are the core of my sleep prescription. But if you've had trouble falling or staying asleep for months, good habits alone usually won't fix it.

For chronic insomnia, the American Academy of Sleep Medicine's 2021 guideline gives its only strong recommendation to cognitive behavioral therapy for insomnia, called CBT-I. It's a structured program, usually 4 to 8 sessions, that retrains how you think about and approach sleep. The same guideline advises against using sleep hygiene tips on their own as the treatment for chronic insomnia. That's why I don't just hand patients a list of tips and send them home.

Talk with your doctor soon if you:

• Snore loudly, or someone has seen you stop breathing or gasp in your sleep
• Wake up with headaches or a dry mouth most mornings
• Have had trouble sleeping three or more nights a week for three months
• Feel an urge to move your legs at night that keeps you awake
• Feel sleepy during the day no matter how long you sleep

Where to start tonight

Pick a wake-up time you can keep every day, weekends included, and count back 8 hours to set your bedtime. Keep it for two weeks before judging how you feel. Consistency does more than any gadget or supplement.

The rest of the plan, from bedroom temperature to caffeine and alcohol timing, is in my sleep prescription. Sleep works best as part of the whole plan, alongside daily movement like the step goal I recommend.

Sources: Watson NF, Badr MS, Belenky G, et al. Recommended amount of sleep for a healthy adult: a joint consensus statement of the American Academy of Sleep Medicine and Sleep Research Society. Journal of Clinical Sleep Medicine. 2015;11(6):591–592. doi:10.5664/jcsm.4758. Edinger JD, Arnedt JT, Bertisch SM, et al. Behavioral and psychological treatments for chronic insomnia disorder in adults: an American Academy of Sleep Medicine clinical practice guideline. Journal of Clinical Sleep Medicine. 2021;17(2):255–262. doi:10.5664/jcsm.8986.