Sleep Across the Lifespan
Duration and architecture both change with age — for different reasons
How much sleep you need, and what that sleep looks like physiologically, both shift substantially across a lifetime. Treating an 8-year-old, a 17-year-old, and a 70-year-old according to the same sleep rules misses real, well-documented biological differences.
Duration Recommendations by Age
A multidisciplinary expert panel convened by the National Sleep Foundation reviewed the evidence base and published consensus duration ranges by age group[13]:
| Age group | Recommended range |
|---|---|
| Newborns (0–3 months) | 14–17 hours |
| Infants (4–11 months) | 12–15 hours |
| Toddlers (1–2 years) | 11–14 hours |
| Preschoolers (3–5 years) | 10–13 hours |
| School-age (6–13 years) | 9–11 hours |
| Teenagers (14–17 years) | 8–10 hours |
| Young adults & adults (18–64 years) | 7–9 hours |
| Older adults (65+ years) | 7–8 hours |
Adolescence: A Genuine Biological Phase Delay
The common assumption that teenagers stay up late purely out of choice or screen habits misses a real physiological shift: puberty is associated with a delay in the circadian release of melatonin, meaning many adolescents genuinely don't feel sleepy until later in the evening than they did as children — while early school start times don't move to accommodate it. The result is a population-level pattern of chronic partial sleep restriction during a developmental window where sleep is particularly important for brain maturation.
Older Adulthood: Less Total Sleep, More Fragmentation
A large meta-analysis of sleep parameters from childhood to old age found that ageing is associated with increased time to fall asleep, a rising proportion of light sleep, and a falling proportion of REM sleep[7]. Older adults also tend to experience a circadian phase advance — feeling sleepy earlier in the evening and waking earlier in the morning — and more fragmented sleep with more nighttime awakenings.
The important nuance: this doesn't mean older adults need meaningfully less sleep — the recommended range only drops modestly, to 7–8 hours. What changes is the body's ability to generate and sustain deep, consolidated sleep, which is why sleep complaints become more common with age even when the underlying need for sleep hasn't dropped much at all. This also means environmental and behavioural fundamentals (Sections 8 and 9) tend to matter more, not less, as people age — there's less physiological slack to compensate for a poor sleep environment or a late caffeine habit.
Section takeaway
Sleep need declines only modestly across adulthood — from roughly 7–9 hours to 7–8 — but sleep architecture becomes measurably lighter and more fragmented with age. A teenager's late bedtime is frequently a real biological phase delay, not just a discipline issue; an older adult's lighter, more fragmented sleep is a real architectural change, not just "needing less."