(Revised and updated from an earlier version.)
At Baby Sleep Science, we like to solve as many problems as we can with as little parental sleep deprivation and hassle as possible.
Understanding and implementing the information in this post—which may seem simple and intuitive at times—can lead to major sleep improvements with very little stress for all involved. Even when further action is required in the form of a personalized sleep consult, an understanding of the sleep drives, sleep environment and sleep safety is critical to the success of your plan. Please review this information carefully.
The families we work with make different choices when it comes to where and how they prefer their baby to sleep, and we support that. We encourage you to make your decision from an informed perspective, weighing the risks and benefits of your options. We always recommend discussing your sleep arrangement choices with your pediatrician and following the current safety recommendations of the American Academy of Pediatrics.
Understanding What Drives Your Child to Sleep
Knowing when your baby is ready for sleep is very important. Sleep pressure and the circadian rhythm are the main drivers of your child’s sleep. These two sleep drives should be working together as you implement your sleep intervention to maximize your success.
Homeostatic (Sleep) Pressure
Sleep pressure is simply the accumulation over time of the need for sleep. In other words, it’s how tired your child is. The longer your child is awake, the sleepier he or she becomes (which doesn’t necessarily mean it’s easier for him or her to fall asleep). Your baby will typically experience the highest sleep pressure at bedtime. When your child has a nap or some night sleep, the sleep pressure wears off a bit, and he or she can stay awake for another stretch of time. The length of time your child sleeps matters: Often, the longer your child has been asleep, the longer he or she can then stay awake. This is why wake-ups in the middle of the night and early-morning can be more challenging problems to solve than those at bedtime. Sleep pressure also determines your baby or toddler’s nap needs, and is what leads to over-tiredness or sleep deficits.
The Circadian Rhythm
The circadian rhythm is your internal biological clock; it controls the timing of many events in your body. Sleep is one of those events, in addition to things such as hormone production, bathroom needs, and meal timing. The circadian rhythm is complex! Because it is controlled by exposure to light and dark, your child’s room environment is important during times of sleep. The circadian rhythm begins to consolidate your newborn’s sleep at night and wakefulness during the day, starting around 6-7 weeks old (usually coinciding with the onset of social smiling). Regular bedtimes pop up around 3 months. By 6 months, it becomes the main force behind your child’s sleep patterns. The circadian rhythm also does some counterintuitive things, such as strongly promoting wakefulness during the Wake Maintenance Zone (the “second wind”) right before it promotes sleep at bedtime. It is important to understand this phenomenon—and what affects it—when choosing the most successful time to begin your sleep intervention.
The circadian rhythm works best with regularity. Wide ranges in bedtimes and wake times can desynchronize the rhythm, which is not helpful to your child during a period of change. For this reason you’ll want to put your baby to bed within the same 30-minute window each night and start her day within the same 30-minute window each morning as often as you can. There are some exceptions to the bedtime rule if sleep pressure is extremely high, but few exceptions, if any, to the regular morning wake time.