Regulators of a great night's sleep. How Sleep Cycles, Sleep Pressure and Circadian Rhythm work together.

Sleep isn't just about rest; it's a vital part of our lives and affects our overall health, brain function, and emotions. For new parents, understanding our body's sleep regulators can make a big difference in helping their babies (and themselves) get a great night's sleep. Let’s explore how sleep works.

What are Sleep Cycles anyway?

For adults, a full sleep cycle lasts about 90 minutes and includes two main types of sleep: NREM (Non-Rapid Eye Movement) and REM (Rapid Eye Movement). NREM sleep helps our bodies recover and strengthens our immune system, while REM sleep, where we dream, supports our emotions and helps our brains learn and remember things. Being able to sleep uninterrupted through all of these sleep stages is important to feel fully rested in the morning and reap all the benefits of sleep.

We go through several sleep cycles each night, with REM periods getting longer towards the morning. A full night of sleep is therefore especially critical for learning and memory. As adults, we wake up briefly during these cycles without even noticing. But for babies, it can be a different story.

In the first six months, babies spend about half of their sleep in REM, making them wake up more easily. Their sleep cycles last 30-50 minutes. If they haven’t learned to fall asleep on their own, they often need your help to get back to sleep and ‘connect their sleep cycles’. If you’re experiencing frequent short naps, you probably know your baby’s sleep cycle down to the minute! After six months, babies sleep becomes more and more similar to adults as they move closer to 90min sleep cycles.

Regulators of a great night's sleep: Circadian Rhythm and Sleep Pressure

Two main processes control sleep: circadian rhythm and homeostatic sleep pressure.

#CircadianRhythm: This is our body’s internal clock, running on a 24-hour cycle. It influences sleep-wake patterns, hormone release, and body temperature. Controlled by a part of the brain sensitive to light and darkness, the circadian rhythm helps us stay alert during the day and sleepy at night. Light exposure, especially from screens, can impact this rhythm. The hormone melatonin rises in the evening to make us sleepy and drops in the morning to help us wake up.

#HomeostaticSleepPressure: This is the body’s need for sleep that builds up the longer we’re awake. It’s driven by the accumulation of a chemical called adenosine, which promotes sleepiness. The longer we stay awake, the more adenosine builds up, increasing our need to sleep. During sleep, adenosine levels drop, reducing sleep pressure.

These two processes work together. For example, your circadian rhythm might tell you it’s bedtime at 10 PM, but if you’ve taken a long nap, your sleep pressure might be low, making it hard to fall asleep. This is why a long nap at daycare can cause bedtime battles with your preschooler! On the other hand, staying up all night raises your sleep pressure, but if it’s daytime, your circadian rhythm will keep you awake. This can be helpful when traveling to different time zones to help your body adjust to the new day/night schedule.

Why do babies need help connecting their sleep cycles?

When babies can connect their sleep cycles, they and their parents benefit from more continuous and restorative sleep. This helps babies with their physical and cognitive development and allows parents to get better rest, improving overall health and well-being.

Babies have immature circadian rhythms and homeostatic sleep pressure mechanisms and often struggle in the beginning to connect sleep cycles, this is where sleep training comes into play. Understanding and managing wake windows—periods during which a baby is awake between naps/sleep—makes sleep training a lot easier as we can utilize our knowledge about these sleep regulators, circadian rhythm and sleep pressure, to achieve optimal sleep.

Knowing all of this, what can you do today?

In the morning, as Dr. Andrew Huberman always says (IYKYK), get outside in the sunlight first thing in the morning every morning to help establish your child’s circadian rhythm. Closer to bedtime, create a dim, calm and cool environment to help with melatonin secretion. By keeping an eye on age-appropriate wake windows, we can utilize babies natural sleep pressure to help them nap and head to bed without becoming overtired and cranky.

If you. are struggling with your baby's sleep, we can help though their entire process. Check out our sleep packages here!