The average adult in the United States sleeps about 7 hours per night, though roughly 35% of adults fall short of that mark and get less than the recommended minimum. Globally, the picture is similar: studies of pre-industrial societies without electricity or screens found an average of just 6 hours and 25 minutes, suggesting humans may have never been the eight-hour sleepers we assume we once were.
Recommended Sleep by Age
Sleep needs change dramatically across the lifespan. The CDC provides these daily recommendations:
- Newborns (0–3 months): 14–17 hours
- Infants (4–12 months): 12–16 hours, including naps
- Toddlers (1–2 years): 11–14 hours, including naps
- Preschoolers (3–5 years): 10–13 hours, including naps
- School-age children (6–12 years): 9–12 hours
- Teenagers (13–17 years): 8–10 hours
- Adults (18–64 years): 7–9 hours
- Older adults (65+): 7–8 hours
These are targets, not averages. Most age groups fall noticeably short of their recommended range, and the gap is especially wide for teenagers.
How Much Teens Actually Sleep
Teenagers average between 7 and 7.25 hours of sleep per night, yet research consistently shows they need about 9.25 hours. That’s a two-hour nightly deficit, which adds up to roughly 14 missing hours every week. Biology works against them: puberty shifts the body’s internal clock later, making it difficult to fall asleep before 11 p.m., while school start times force early wake-ups. The result is that most teens are chronically underslept throughout the school year.
Sleep Patterns in Older Adults
Older adults need about the same total sleep as younger adults, somewhere between 7 and 9 hours. But the way they sleep shifts noticeably. Sleep becomes lighter, with less time spent in the deeper stages that feel most restorative. Waking up during the night becomes more common, and the whole sleep window tends to shift earlier, with earlier bedtimes and earlier wake-ups. These changes are a normal part of aging, not a sign that older adults need less sleep.
The Eight-Hour Myth
There’s a widespread belief that modern life has stolen sleep from us, that our ancestors slept eight or nine hours before electricity and screens ruined everything. A study from UCLA that tracked sleep patterns in three pre-industrial societies (groups in Tanzania, Namibia, and Bolivia with no access to artificial light) found the opposite. These groups averaged 6 hours and 25 minutes per night, placing them at the low end of what adults in industrialized countries report. The lead researcher noted that removing modern technology doesn’t automatically produce longer sleep. Humans may simply be wired for less sleep than popular wisdom suggests.
That said, 6.5 hours still falls below the 7-hour minimum that major health organizations recommend based on disease risk data. The fact that our ancestors slept this amount doesn’t necessarily mean it’s optimal.
What Cuts Into Sleep
Work schedules are one of the biggest factors. Among people who work regular daytime hours, about 26% sleep six hours or less. For night shift workers, that number nearly doubles to 50%. Early morning shifts and rotating schedules carry similarly high rates of short sleep, hovering around 49%. If you work outside of standard daytime hours, the odds of getting enough sleep drop significantly.
Geography plays a role too, at least in the U.S. The southeastern states and the Appalachian region consistently report the lowest rates of healthy sleep duration, while people in the Great Plains states fare better. These patterns likely reflect differences in work types, income, health conditions, and access to healthcare rather than anything about the locations themselves.
Sleep Efficiency Matters Too
Total time in bed isn’t the same as total time asleep. Sleep efficiency, the percentage of time in bed that you’re actually sleeping, is a useful way to think about quality. A healthy sleep efficiency falls between 85% and 90%. That means if you’re in bed for 8 hours, spending 6.5 to 7.2 of those hours asleep is normal. The rest is time falling asleep, brief nighttime awakenings, and waking up before you get out of bed. If you find yourself lying awake for long stretches, your efficiency may be lower than typical, even if your total time in bed looks fine on paper.
Health Risks of Falling Short
The consequences of consistently sleeping too little go well beyond feeling tired. Sleeping only five to six hours per night doubles the risk of developing prediabetes or type 2 diabetes compared to sleeping seven to eight hours. People who sleep four hours or fewer are twice as likely to have high blood pressure. And middle-aged adults who combine short sleep (under six hours) with other sleep problems, like frequent waking or difficulty falling asleep, face nearly triple the risk of heart disease.
Mental health takes a hit as well. Adults with a history of insomnia are four times more likely to develop major depression within three years. In teenagers, the link is even more striking: sleep problems preceded the onset of depression 69% of the time and anxiety disorders 27% of the time. Sleep trouble isn’t just a symptom of mental illness. It often comes first.
The productivity costs are substantial. Insomnia alone costs the U.S. workforce an estimated $63.2 billion per year in lost productivity, averaging about 11.3 lost workdays per affected worker annually. That figure, from a Harvard Medical School analysis, counts only the reduced focus and performance of people who show up to work underslept, not absenteeism.
What “Enough” Looks Like
Seven hours is the floor recommended for adults, not the ceiling. Most adults function best somewhere in the 7 to 9 hour range, and where you fall within that range is partly genetic. A practical way to gauge your own need: on a stretch of days without an alarm (a vacation, for example), note when you naturally wake up feeling alert. That duration, after a few days of catching up on any accumulated sleep debt, is a reasonable estimate of your personal target. If you consistently need an alarm to wake up, feel drowsy during the afternoon, or fall asleep within minutes of lying down, you’re likely getting less sleep than your body requires.