Most adults need at least 7 hours of sleep per night, with 7 hours linked to the lowest risk of early death and chronic disease. But the exact number depends on your age, and the quality of those hours matters nearly as much as the quantity.
Recommended Sleep by Age
The CDC breaks sleep recommendations into nine age groups. For children, the totals include naps:
- Newborns (0–3 months): 14–17 hours
- Infants (4–12 months): 12–16 hours
- Toddlers (1–2 years): 11–14 hours
- Preschoolers (3–5 years): 10–13 hours
- School-age children (6–12 years): 9–12 hours
- Teens (13–17 years): 8–10 hours
- Adults (18–60 years): 7 or more hours
- Adults (61–64 years): 7–9 hours
- Adults (65 and older): 7–8 hours
Notice that the range narrows as you age. A teenager legitimately needs up to 10 hours, while an older adult generally tops out at 8. These aren’t aspirational targets. They reflect the amount of sleep your body needs to complete the biological processes that happen only while you’re unconscious.
Why 7 Hours Keeps Coming Up
A large meta-analysis published in the Journal of the American Heart Association found a clear U-shaped relationship between sleep duration and mortality. Seven hours per night sat at the bottom of the curve, meaning the lowest risk. Sleeping less than 7 hours raised the risk of early death by about 6% for every hour lost. Sleeping more than 7 hours raised it by about 13% for every extra hour. At 6 hours, the increased risk was minimal (around 1%), but by 9 hours, the relative risk jumped to 15% higher than the 7-hour baseline.
That doesn’t mean 9 hours of sleep causes harm. Consistently long sleep often signals an underlying condition like sleep apnea, depression, or chronic inflammation rather than being dangerous on its own. But the data consistently points to 7 as the sweet spot for adults.
What Happens During Those Hours
Sleep isn’t a single uniform state. Your brain cycles through distinct stages roughly every 90 minutes, and each one does different work. About 5% of your night is spent in the lightest stage, a brief transition into sleep. Stage 2, a slightly deeper phase, takes up around 45% of total sleep time. Deep sleep (stage 3) accounts for about 25%, and REM sleep, when most dreaming occurs, fills the remaining 25%.
Deep sleep is where your body does its heaviest physical repair. It’s also when your brain’s waste-removal system, sometimes called the glymphatic system, is most active. During deep sleep, the spaces between brain cells physically expand, allowing cerebrospinal fluid to flush out metabolic waste more efficiently. That waste includes proteins like amyloid-beta and tau, which are linked to neurodegenerative disease when they accumulate. Cut your sleep short and this cleaning process gets less time in its most active phase.
REM sleep, which increases in later sleep cycles, plays a central role in memory consolidation and emotional regulation. People who consistently wake up after 5 or 6 hours tend to lose a disproportionate amount of REM sleep because they’re cutting off the end of the night, when REM periods are longest.
What Short Sleep Does to Your Body
Even modest sleep restriction has measurable metabolic effects. A study from the American Diabetes Association found that healthy men who slept only 5 hours a night for one week experienced a 20% drop in insulin sensitivity, the body’s ability to regulate blood sugar efficiently. That’s a meaningful shift toward the kind of metabolic dysfunction that precedes type 2 diabetes, and it happened in just seven days.
Short sleep also increases appetite. When you’re underslept, your body produces more of the hormone that signals hunger and less of the one that signals fullness. Combined with reduced insulin sensitivity, this creates a metabolic environment that promotes weight gain even without any change in diet or exercise.
Weekend Catch-Up Sleep Doesn’t Work
Sleeping in on Saturday and Sunday feels restorative, but the metabolic damage from a week of short sleep doesn’t reverse that easily. Researchers at the University of Colorado tested this directly by putting participants through cycles of 5-hour sleep nights followed by two days of recovery sleep. The result: recovery sleep provided no metabolic benefit over continuous sleep deprivation. Participants in the catch-up group gained an average of about 3 pounds over the two-week study and experienced a 27% decrease in insulin sensitivity.
Even more concerning, the catch-up group showed reductions in liver and muscle insulin sensitivity that weren’t seen in the group that was simply sleep-deprived the entire time. The researchers found that bouncing between sleep deprivation and recovery actually disrupted participants’ internal body clocks further when they returned to short sleep. In other words, the pattern many people follow (grinding through the workweek, then sleeping late on weekends) may be worse than consistently short sleep in some respects.
Sleep Needs for Athletes and Active People
If you exercise intensely or play competitive sports, you likely need more than the standard 7-hour minimum. Expert consensus recommendations published in the British Journal of Sports Medicine suggest that while 7 to 9 hours is appropriate for healthy adults, athletes may need additional sleep to recover from the physical and psychological demands of training. For teenage athletes, 8 to 10 hours is recommended.
One study of trained endurance athletes found that three consecutive nights of extended sleep (about 8.4 hours) improved performance compared to their habitual 6.8 hours. The researchers recommended that endurance athletes aim for more than 8 hours per night. This makes sense physiologically: growth hormone release peaks during deep sleep, and tissue repair accelerates when the body is at rest.
How Naps Fit In
Naps can supplement nighttime sleep, but timing and length matter. A nap of 20 minutes or less keeps you in lighter sleep stages, boosting alertness for a couple of hours afterward without making you groggy or interfering with your ability to fall asleep that night. If you have more time, a 90-minute nap allows you to complete a full sleep cycle and wake up from a lighter stage, minimizing grogginess.
The worst nap length is around 60 minutes. At that point you’re likely deep in stage 3 sleep, and waking up mid-cycle can leave you feeling significantly worse than before you lay down. That heavy, disoriented feeling is called sleep inertia, and it can take 15 to 30 minutes to clear even after a well-timed nap. After a poorly timed one, it can linger much longer.
Signs You’re Not Getting Enough
Many people who sleep 5 or 6 hours believe they’ve adapted to it, but performance testing consistently shows otherwise. Common signs of insufficient sleep include needing an alarm to wake up every morning, feeling drowsy during the afternoon, falling asleep within minutes of lying down (healthy sleep onset takes 10 to 20 minutes), and relying on caffeine to function past midday. Difficulty concentrating, increased irritability, and catching colds more frequently are also tied to chronic short sleep.
If you’re sleeping 7 to 8 hours and still feel exhausted, the issue is more likely sleep quality than quantity. Frequent awakenings, snoring, or gasping during sleep may indicate a condition like sleep apnea that fragments your sleep cycles and reduces the time you spend in the restorative deep and REM stages.