Healthy adults need at least seven hours of sleep per night. That’s the consensus recommendation from both the American Academy of Sleep Medicine and the Sleep Research Society, based on a panel of 15 experts who reviewed the evidence on sleep duration and health outcomes. Children and teenagers need significantly more, with requirements decreasing gradually from infancy through adolescence.
Sleep Needs by Age
Sleep requirements shift dramatically over a lifetime. Newborns and very young infants have such wide variation in sleep patterns that no single recommendation applies. Starting at four months, though, the numbers become clearer:
- Infants (4 to 12 months): 12 to 16 hours
- Toddlers (1 to 2 years): 11 to 14 hours
- Preschoolers (3 to 5 years): 10 to 13 hours
- School-aged children (6 to 12 years): 9 to 11 hours
- Teenagers (13 to 18 years): 8 to 10 hours
- Adults (18 and older): at least 7 hours
These ranges are per 24-hour period, which matters for younger children who still nap. A toddler sleeping 10 hours at night and napping for two hours during the day is right on target. For school-aged kids and older, though, almost all sleep happens at night.
Why Seven Hours Is the Adult Floor
The expert consensus panel was direct: six hours or fewer is inadequate to sustain health and safety in adults. That applies from age 18 through the end of life, not just to younger adults. The seven-hour minimum holds whether you’re 25 or 75.
Your body cycles through distinct sleep stages roughly every 80 to 100 minutes. A typical night includes four to six of these cycles, each containing light sleep, deep sleep, and dreaming sleep. Deep sleep is when your body does its most intensive physical repair and memory consolidation. Dreaming sleep supports emotional processing and creative problem-solving. Cutting your night short doesn’t just reduce total rest; it eliminates entire cycles, which disproportionately strips away the types of sleep your brain prioritizes later in the night.
Most healthy adults land somewhere between seven and nine hours. Some people genuinely feel sharp and rested at seven, while others need closer to nine. The key distinction is between feeling functional on caffeine and actually being well-rested. If you need an alarm clock every morning and feel drowsy by mid-afternoon, you’re likely not getting enough.
What Happens When You Sleep Too Little
Chronically sleeping under seven hours carries real health costs. A large systematic review found that short sleep duration was associated with a 45% increased risk of coronary heart disease. That’s a substantial jump, comparable to some well-known cardiovascular risk factors. Both short and long sleep are also linked to higher body mass index and more depressive symptoms compared to people sleeping seven or eight hours.
The cognitive effects are equally striking. Sleeping six hours or less per night is associated with impaired memory and an increase in amyloid-beta, a protein that forms brain plaques characteristic of Alzheimer’s disease. This isn’t just about feeling foggy the next day. Chronic short sleep appears to accelerate the kind of brain changes associated with long-term cognitive decline.
How Sleep Changes as You Age
Older adults often assume they simply need less sleep. The biology tells a different story. The recommended minimum stays at seven hours regardless of age. What changes is your ability to get that sleep in one uninterrupted stretch.
As you age, total sleep time decreases by roughly 10 minutes per decade. You spend less time in deep sleep, wake up more often during the night, and generally have lower sleep efficiency, meaning a larger portion of time in bed is spent awake. These are normal changes, not signs that your body has stopped needing rest. The sleep need remains; the architecture just becomes more fragmented. Many older adults compensate by napping during the day, which can work as long as total sleep across 24 hours still reaches the seven-hour threshold.
Can You Train Yourself to Need Less Sleep?
A very small number of people carry a genetic variant that allows them to function normally on six hours or less. This trait is genuinely rare. If you’ve slept short your entire life and have never felt the effects, you may be one of them. But the vast majority of people who claim to thrive on five or six hours have simply adapted to feeling impaired. Chronic sleep deprivation blunts your awareness of how impaired you actually are, creating an illusion of adequacy.
You cannot train yourself into needing less sleep any more than you can train yourself into needing less water. Tolerance to the feeling of sleepiness is not the same as tolerance to the biological damage of insufficient sleep. The cardiovascular and cognitive risks accumulate whether or not you feel tired.
Recovering From Lost Sleep
Sleep debt is real, and paying it back isn’t as simple as sleeping in on weekends. One good night can’t erase the deficit from several short nights. How long recovery takes depends on how severe and how prolonged the deprivation has been. A single rough night can be offset by sleeping a bit longer the next night or two. Weeks or months of insufficient sleep take considerably longer to resolve, and some research suggests that certain cognitive effects may persist even after sleep duration normalizes.
The most effective strategy is consistency. Going to bed and waking up at roughly the same time each day, including weekends, helps your body’s internal clock regulate sleep stages efficiently. If you’re currently averaging six hours and want to move toward seven or eight, shifting your bedtime earlier by 15 to 20 minutes every few days is more sustainable than a sudden change. Your body adjusts to the new schedule within a week or two, and the difference in daytime alertness is often noticeable within days.