Most adults need 7 to 9 hours of sleep per night, with 7 hours being the minimum linked to good health outcomes. Children and teens need significantly more. But the right amount varies by age, and hitting a specific number of hours matters less than you might think if the sleep you’re getting is low quality.
Recommended Hours by Age
The CDC breaks sleep recommendations into nine age groups, and the ranges shift dramatically from birth through adulthood:
- Newborns (0 to 3 months): 14 to 17 hours
- Infants (4 to 12 months): 12 to 16 hours, including naps
- Toddlers (1 to 2 years): 11 to 14 hours, including naps
- Preschoolers (3 to 5 years): 10 to 13 hours, including naps
- School-age children (6 to 12 years): 9 to 12 hours
- Teens (13 to 17 years): 8 to 10 hours
- Adults (18 to 60 years): 7 or more hours
- Older adults (61 to 64 years): 7 to 9 hours
- Adults 65 and older: 7 to 8 hours
Notice that the recommendation narrows as you age. A 70-year-old who sleeps 7 hours is right in the sweet spot, while a teenager getting the same amount is consistently undersleeping. For children under 5, naps count toward the daily total, so a toddler sleeping 10 hours at night plus a 2-hour nap is within range.
Why 7 Hours Keeps Showing Up
A large meta-analysis published in the Journal of the American Heart Association found a U-shaped relationship between sleep duration and the risk of death and cardiovascular disease. The lowest risk point sat at roughly 7 hours per night, and this held true for both men and women. Sleeping significantly less than 7 hours raised the risk, but so did regularly sleeping much longer.
That doesn’t mean 8 or 9 hours is dangerous. The National Heart, Lung, and Blood Institute notes that sleeping more than 9 hours isn’t necessarily harmful, and it can be genuinely beneficial for young adults, people recovering from sleep loss, and anyone fighting off illness. The concern with very long sleep is that it sometimes signals an underlying health problem rather than causing one directly.
Quality Matters as Much as Quantity
You can spend 8 hours in bed and still feel terrible if the sleep itself is fragmented. The American Heart Association identifies several markers of sleep quality: how long it takes you to fall asleep, how often you wake during the night, how long those awakenings last, and whether you wake earlier than intended. Frequent disruptions from conditions like sleep apnea also erode quality even when total time looks adequate on paper.
One reason quality matters so much is your brain’s waste-clearing system, sometimes called the glymphatic system. During deep sleep, fluid washes through brain tissue, collecting metabolic waste and draining it out through channels around blood vessels. This process works best during deep, slow-wave sleep, the stage when the spaces between brain cells expand and allow fluid to flow more efficiently. If your sleep is shallow or constantly interrupted, this cleanup process gets shortchanged regardless of how many hours you log.
How to Tell If You’re Getting Enough
The simplest test is how you feel during the day. If you can sit through a meeting, read a chapter of a book, or ride as a passenger in a car without fighting the urge to doze off, you’re likely sleeping enough. Clinicians sometimes use a tool called the Epworth Sleepiness Scale to put a number on this. It scores your likelihood of dozing in eight common situations on a scale of 0 to 24. A score of 0 to 10 falls in the normal range. Anything above 11 suggests excessive daytime sleepiness that warrants a closer look, with scores of 16 to 24 indicating severe sleepiness.
You don’t need a formal assessment to notice the signs. Needing an alarm clock every single morning, feeling groggy for more than 20 to 30 minutes after waking, or relying on caffeine just to function through the afternoon are all practical signals that your sleep is falling short in duration, quality, or both.
Some People Genuinely Need Less
A small number of people function perfectly on 6 hours or fewer per night without any caffeine crutches or daytime fatigue. This is called short sleeper syndrome, and it appears to be genetic. Researchers have identified changes in two specific genes, DEC2 and ADRB1, that allow these individuals to feel fully rested on less sleep. True short sleepers have been this way their entire lives. They don’t force themselves to sleep less; they simply wake up naturally and feel fine.
This condition is rare, and most people who think they’re short sleepers are actually running on a sleep deficit they’ve grown accustomed to. If you need coffee to get through the day or crash hard on weekends, that’s a sign you’re sleep-deprived rather than genetically wired for less sleep.
Sleep Needs During Pregnancy
Pregnancy changes sleep needs and sleep quality in ways that shift across trimesters. In the first trimester, rising progesterone levels often cause intense drowsiness. The second trimester typically brings some relief. By the third trimester, physical discomfort and nasal swelling driven by high estrogen levels make it harder to sleep deeply, and some women develop snoring or obstructive sleep apnea for the first time.
Research from Johns Hopkins Medicine links insufficient sleep during pregnancy to higher rates of preeclampsia, gestational diabetes, longer labors, and increased likelihood of cesarean delivery. Women getting fewer than 6 hours over a 24-hour period face the highest risk. Prioritizing sleep during pregnancy isn’t just about comfort; it has measurable effects on outcomes for both mother and baby.
Sleep and Physical Performance
Athletes and highly active people sometimes assume they can push through on less sleep, but the data points the other direction. Both the International Olympic Committee and the NCAA recommend at least 7 hours for adult athletes, with many sports scientists suggesting 8 to 10 hours for peak recovery.
Sleep deprivation impairs reaction time, decision-making, coordination, and the ability to process information quickly. It also slows muscle recovery and reduces endurance. Athletes sleeping fewer than 6 hours per night face a significantly higher risk of injury, partly because sleep loss weakens the neuromuscular control that keeps joints stable and increases systemic inflammation. The risk extends to concussions, since impaired motor coordination and compromised balance make athletes more vulnerable to head injuries.
Even if you’re not a competitive athlete, these effects scale down to everyday physical activity. Adequate sleep makes your workouts more productive, your coordination sharper, and your recovery faster.
Can You Make Up for Lost Sleep?
Sleeping in on the weekend after a bad week feels restorative, and to some extent it is. Your brain’s waste-clearing system can catch up on missed deep sleep cycles, and some cognitive deficits from short-term sleep loss improve with recovery sleep. But the relationship isn’t one-to-one. Losing 10 hours of sleep over a week doesn’t mean sleeping 10 extra hours on Saturday fixes everything.
Chronic sleep debt, the kind that accumulates over months or years, is harder to reverse. The metabolic, cardiovascular, and cognitive effects of long-term undersleeping don’t fully disappear after a few good nights. The most effective strategy is consistent, adequate sleep most nights rather than cycling between deprivation and recovery.