Most adults need at least 7 hours of sleep per night. The CDC recommends 7 or more hours for adults aged 18 to 60, 7 to 9 hours for those 61 to 64, and 7 to 8 hours for people 65 and older. Children and teenagers need significantly more.
Recommended Sleep by Age
Sleep needs change dramatically across a lifetime. Newborns (0 to 3 months) need 14 to 17 hours a day. Infants 4 to 12 months old need 12 to 16 hours including naps, and toddlers (1 to 2 years) need 11 to 14 hours. Preschoolers require 10 to 13 hours, and school-age kids (6 to 12) need 9 to 12 hours.
Teenagers between 13 and 17 need 8 to 10 hours, which is more than most of them actually get once school schedules, homework, and screens enter the picture. By adulthood, the 7-hour floor stays consistent into old age, though the upper end of the range narrows slightly. A 70-year-old who sleeps 7 to 8 hours is right on target.
Why 7 Hours Is the Floor, Not the Goal
Seven hours is the minimum for most adults, not the sweet spot. During sleep, your brain runs a waste-clearance system that flushes out metabolic byproducts. Cerebrospinal fluid flows through brain tissue, picks up waste, and drains it into the lymphatic system in your neck. This process works best during deep sleep, when the spaces between brain cells physically expand, allowing fluid to move more efficiently. Cutting your sleep short means cutting this cleanup short.
Adults should spend roughly 20% of their total sleep time in deep sleep. For an 8-hour night, that translates to about 60 to 100 minutes. If you’re only sleeping 5 or 6 hours, you’re compressing or losing portions of deep sleep and REM sleep, since both stages become more concentrated in the later hours of the night.
What Happens When You Don’t Get Enough
Sleeping fewer than 6 hours a night consistently raises cardiovascular risk. One study of nearly 4,000 participants found that short sleepers had 27% higher odds of early plaque buildup in their arteries compared to those sleeping 7 to 8 hours. That’s not a distant, abstract risk. It’s measurable changes in blood vessel health happening in otherwise healthy people.
Beyond heart health, chronic short sleep impairs blood sugar regulation, increases weight gain, weakens immune function, and degrades memory consolidation. The cognitive effects are especially deceptive: people who are chronically sleep-deprived often stop noticing how impaired they are, rating their own alertness as normal even as their reaction times and decision-making measurably decline.
Too Much Sleep Carries Risks Too
Consistently sleeping 9 or more hours is also linked to worse health outcomes. A large prospective study found that people sleeping 9 or more hours had a 74% higher risk of all-cause mortality and an 81% higher risk of cardiovascular death compared to those sleeping 7 to 8 hours. This doesn’t necessarily mean long sleep causes these problems. In many cases, oversleeping is a signal that something else is going on, like depression, sleep apnea, chronic pain, or another underlying condition that fragments sleep and makes it less restorative.
If you’re regularly sleeping 9 or more hours and still feeling tired, that pattern is worth investigating rather than assuming you simply need more rest.
Weekend Catch-Up Sleep Doesn’t Work
A common strategy is to shortchange sleep during the workweek and make up for it on weekends. Research from the NIH shows this backfires. In a controlled study, participants who tried weekend recovery sleep after five days of restriction gained an average of about 3 pounds and experienced a 27% decrease in insulin sensitivity, a key marker of metabolic health. Recovery sleep didn’t just fail to reverse the damage. It appeared to make certain metabolic measures worse than continuous sleep deprivation, particularly in the liver and muscles.
The takeaway is straightforward: you can’t bank sleep or pay off a sleep debt with a single long weekend. Consistent nightly sleep is what your body needs.
Some People Genuinely Need Less Sleep
You may know someone who claims to thrive on 5 hours a night. In rare cases, this is real. Researchers have identified at least seven genes associated with “natural short sleep,” a trait that allows certain people to function fully on just 4 to 6 hours. The first gene discovered was DEC2, found in a family of naturally short sleepers. Since then, mutations in genes like ADRB1, NPSR1, and GRM1 have been linked to the same ability across multiple unrelated families.
This trait is genuinely rare. Most people who think they’re fine on little sleep are actually chronically sleep-deprived and have simply adapted to how that feels. If you need an alarm clock to wake up, feel drowsy in the afternoon, or fall asleep within minutes of your head hitting the pillow, you’re likely not getting enough.
How to Tell if You’re Getting Enough
One useful self-check is the Epworth Sleepiness Scale, a simple questionnaire that scores your daytime drowsiness from 0 to 24. A score of 0 to 10 indicates normal daytime alertness. Scores of 11 to 12 suggest mild excessive sleepiness, 13 to 15 is moderate, and 16 to 24 is severe. You can find it with a quick search and complete it in under two minutes.
Beyond questionnaires, pay attention to practical signals. Are you relying on caffeine to get through the afternoon? Do you drift off during meetings or while watching TV in the evening? Do you sleep significantly longer on days off than on workdays? A gap of more than an hour between your free-day and workday sleep duration is a strong sign of accumulated sleep debt.
Practical Ways to Protect Your Sleep
Your body’s sleep drive is regulated in part by melatonin, a hormone your brain releases in response to darkness. Even ordinary indoor lighting (around 90 lux, the level in a typical living room) can suppress melatonin production and delay when you feel sleepy. Dimming your lights in the hour or two before bed gives your brain a head start on winding down. Bright screens close to bedtime have the same suppressive effect.
Consistency matters more than any single night. Going to bed and waking up at roughly the same time every day, including weekends, reinforces your body’s internal clock and makes it easier to fall asleep and wake naturally. If you’re short on sleep during the day, a nap of 20 to 40 minutes can restore alertness without the grogginess that comes from longer naps that push you into deep sleep.
The 7-hour recommendation isn’t arbitrary. It’s the point below which measurable harm to cardiovascular, metabolic, and cognitive health begins to appear in study after study. For most adults, 7 to 9 hours is the range where your body can complete the full cycle of repair, memory consolidation, and waste clearance it needs to function well the next day.