DP 3 sleep across lifespan

 Overall pattern

• Total sleep decreases with age: about 16 hours at birth → ~6 hours in later adulthood.

• REM sleep is highest in newborns and decreases during early development.

• From adolescence onwards, REM remains fairly stable at around 20–25% of total sleep.

• Deep NREM3 sleep decreases significantly with age, especially from adulthood onwards.

• Sleep becomes increasingly fragmented in older adulthood, with more awakenings and daytime naps.

Birth–2 months

• Sleep is irregular, with sleep occurring at any time.

• About 16 hours/day of sleep.

• Around 50% is REM sleep.

• Infants can enter sleep directly through REM, rather than NREM1.

• Bottle-fed babies tend to sleep for longer periods than breastfed babies.

2–3 months

• Melatonin production becomes cyclical.

• More wakefulness during the day.

• Longer sleep periods at night.

3 months

NREM–REM cycles become more regular.

6 months

• Total sleep decreases slightly.

• Longest nighttime sleep period increases to around 5–8 hours.

12 months

About 14–15 hours of sleep, including 1–2 daytime naps.

Children

• Sleep gradually decreases from about 13 → 11 hours between ages 2–5.

• Decrease is influenced by:

  • Biological maturation

  • Less daytime napping

  • Preschool routines

  • Social factors, including where and with whom children sleep

• REM decreases, while NREM increases.

• More time is spent in NREM2 and NREM3.

Adolescents

• Sleep duration continues to decrease.

• Deep NREM3 decreases, while NREM2 increases.

• Adolescents commonly get less sleep than they need.

• A biological shift in the circadian rhythm delays sleep onset by about 1–2 hours.

• Lifestyle factors also contribute to later bedtimes.

• Sleep patterns are often more irregular across the week.

• By mid-adolescence, sleep patterns become increasingly similar to those of young adults.

Adults

• Adults average around 8 hours of sleep.

• Around 20–25% is REM sleep.

• With increasing age:

  • Total sleep duration decreases.

  • REM sleep decreases somewhat.

  • NREM3/deep sleep decreases significantly.

• From ages 20–60, deep sleep declines by approximately 2% per decade.

• By around age 60, people may have about half as much NREM3 as they did at age 20.

Older Adults

• Sleep becomes more fragmented, with more nighttime awakenings.

• People tend to:

  • Become sleepy earlier in the evening

  • Wake earlier in the morning

  • Take more daytime naps

• Changes may be related to:

  • Age-related deterioration of the SCN/biological clock

  • Reduced melatonin production

  • Medical problems

  • Reduced mobility/exercise

  • Daytime napping

  • Irregular meal times

  • Less consistent exposure to environmental cues/zeitgebers

 REM vs NREM Across Life

Age	Total sleep	REM
Newborn	~16 hrs	~50%
~2 years	~12–13 hrs	20–25%
Childhood/adolescence	~9 hrs	~20–25%
Adulthood	~8 hrs	~20–25%
Later adulthood	~6 hrs	~20–25%