How does your circadian rhythm change with age?

Short answer: It shifts across life. Babies build a day and night rhythm over their early months, children are early types, and teenagers drift later until about age 20, after which the body clock moves earlier again with age. In older age, sleep tends to come earlier with more night waking, and the daily rhythm is often weaker.

When does the circadian rhythm develop in babies?

A newborn's daily rhythms take a few months to settle. Most newborns are asleep more than they are awake, their total daily sleep can be around 18 hours, and they wake in the night because they need feeding.

In a study that followed 35 healthy babies at home, day and night hormone rhythms appeared at about 8 to 9 weeks, at the same time as night-time sleep became established. Other daily rhythms, such as a drop in body temperature at the start of night-time sleep, followed by about 10 to 11 weeks. Parents can help a baby learn the difference: the NHS suggests open curtains and play during the day, and low lights and quiet voices at night.

Why do teenagers stay up late?

Biology plays a big part, alongside psychological and social pressures. Around puberty the body clock shifts later, and the pressure to sleep that builds up during the day builds more slowly, so more mature teenagers may find it easier to stay awake longer. A similar later shift around puberty has been seen in several other mammals, which suggests a built-in change.

Teenagers still need plenty of sleep. The loss of sleep through the teenage years is not driven by a lower need for it, so early school starts that clash with a late body clock can leave many of them short of sleep.

Does chronotype change with age?

Yes, in a clear pattern. In a database of about 25,000 people, mainly from Germany and Switzerland, children were early types and became progressively later through development, reaching their latest timing at around age 20. After that, they became earlier again with increasing age. Women reached their latest point at about 19.5 years and men at about 21.

Your place compared with people of your own age and sex tends to stay the same through life. The data compare people of different ages, but people's memories of their own childhood and teenage timing fit the same pattern. For more on types, see what a chronotype is.

Does the circadian rhythm change in older adults?

Yes. The most prominent change is that sleep moves to earlier hours, often earlier than people would like, and night sleep has more awakenings. Many studies also report a weaker daily rhythm with age, such as a smaller daily rise and fall in body temperature.

The internal day itself does not seem to get shorter, since careful lab studies found no difference in its length between healthy young and older adults. Why sleep moves earlier is still largely unknown, though brain changes and daily life both seem to play a part: less physical activity and less time spent outdoors also affect circadian rhythms.

What helps a body clock at any age?

Light and activity at the right times. Daylight in the day, darker evenings and daytime movement all act as cues that help the clock tell day from night. In care homes, very broken sleep and wake patterns in older adults are linked with very little bright light, and raising indoor light levels has, in some cases, helped sleep settle into longer blocks.

For practical steps, read how to reset your circadian rhythm and why a regular sleep schedule matters.

How Actogram looks at this

Actogram reads the daily rhythm of rest and activity from ordinary minute-level step counts from a phone or watch, and it reads that rhythm from the daytime activity pattern, not only from night sleep. The method was tested on existing data from about 30,000 participant samples from the US NHANES health survey and Fitbit, and testing with academic partners is the next step. Today its tools are for research and wellness use and do not diagnose, treat or prevent any condition.

Sources

• Getting rhythm: how do babies do it?, Archives of Disease in Childhood: Fetal and Neonatal Edition, 2015
• Helping your baby to sleep, NHS, 2025
• Sleep in adolescents: the perfect storm, Pediatric Clinics of North America, 2011
• A marker for the end of adolescence, Current Biology, 2004
• Aging and Circadian Rhythms, Sleep Medicine Clinics, 2015
• How Sleep Works: Your Sleep/Wake Cycle, National Heart, Lung, and Blood Institute, 2022

General information, not medical advice. If sleep or tiredness problems affect your daily life, talk to a doctor. Reviewed 6 November 2026 by the Actogram team.