The body clock: baby sleep regulator #1

What is our body clock and why is it so important for your little one's sleep?

Our body clock is a cluster of nerve cells deeply buried on the undersurface of the brain. The body clock drives our circadian system, which controls the many cyclic changes occuring in human bodies over a 24-hour period. These include the cycles of sleep and wakefulness.

Humans can’t make sleep happen. Sleep isn’t under conscious control. This is why we can't teach babies to sleep. It’s also why you can’t train your baby to sleep better (though you might hear people saying you can)! It's why sleep isn't controlled by sleep associations.

Whether we're adults or children, sleep is controlled by just two biological regulators, the body clock and sleep pressure.

What are the main things to know about the body clock so that your baby's sleep is as easy as possible?

To have healthy sleep patterns, your small child's body clock needs to synchronise with your own. Your and your baby’s body clock also need to synchronise with day and night. Your baby’s body clock is set by the experiences of

• Daylight, noise and activity during the day

• Darkness, quietness and less activity during the Big Sleep at night.

For all of us, and also for your baby, light falling on the back of our eyes has by far the most powerful effect upon the settings of the body clock.

Here are useful things to know about working with your baby's body clock to keep sleep healthy in your family.

• The most important way to set our body clock is to get up at the same time each day. You might hear that regular bedtimes are essential for healthy childhood sleep, but this misunderstands the sleep science! A regular get up time is essential for healthy sleep, at least if any sleep problems have come up. Bedtimes then follow the rise of sleep pressure.

• When your baby is born, her body clock is immature. There are a number of things that you can do to help your baby’s body clock quickly mature and get in sync with your own, so that your baby’s sleep is better consolidated at night. It's normal for newborns, babies and toddlers to wake a few times in the night, though.

• A very fragmented sleep pattern, which I refer to as excessive night waking, is the most common sign of disrupted body clock settings. If your baby is waking excessively at night, there are things you can do to reset your baby’s body clock so that it is in better sync with your own. This means understanding how your baby's sleep pressure works, too.

• When you have a baby, evening is best thought of as an extension of daytime. In climates with long winter nights, night-times are less likely to be disrupted with excessive waking if the evenings are filled with (artificial) light, noise and activity. This keeps your little one dialled down as his sleep pressure rises.

• It takes a couple of weeks to reset your baby's body clock.

These things might sound surprising to hear, and quite different to other approaches. But they are the key steps to The Possums Sleep Program.

(You can take a deeper dive into the science of the body clock here, but if you are needing help for your little one's sleep, you might leave that deeper dive for later.)

Selected references

Borbély AA. A two process model of sleep regulation. Hum Neurobiol. 1982;1(3):195–204.

Jenni OG, Carskadon MA. Sleep behavior and sleep regulation from infancy through adolescence: normative aspects. Sleep Medicine Clinics. 2007;2(321-329).

Gallaher KGH, Slyepchenko A, Frey BN, Urstad K, Dorheim SK. The role of circadian rhythms in postpartum sleep and mood. Sleep Medicine Clinics. 2018;13(3):359-374.

Lillis TA, Hamilton NA, Pressman SD, Khou CS. The association of daytime maternal napping and exercise with nighttime sleep in first-time mothers between 3 and 6 months postpartum. Behav Sleep Med. 2016:doi:10.1080/15402002.15402016.11239580.

Wong SD, Wright KP, Spencer RL. Development of the circadian system in early life: maternal and environmental factors. Journal of Physiological Anthropology. 2022;41(22):https://doi.org/10.1186/s40101-40022-00294-40100.

Yoshida M, Ikeda A, Adachi H. Contributions of light environment and co-sleeping to sleep consolidation into nighttime in early infants: a pilot study. Early Human Development. 2024;189:105923.