(Revised and updated from an earlier version.)
It seems that sleep advice for babies and toddlers is contradictory and confusing. Some sleep experts insist that the only way for a baby to have quality sleep is with a super-early bedtime and a long nighttime sleep duration, while others insist that later bedtimes and shorter sleep durations are better. If you do a quick survey of your friends who have children, you’ll undoubtedly hear from people who swear—quite vehemently—by one approach or another. Here’s the truth: a stable schedule with regular bed/wake/nap times is best; timing doesn’t matter! As long as your child is getting enough sleep (check out our age-by-stage sleep chart), then an early or late bedtime is fine as long as it suits your family's schedule. Sleeping from 9pm to 8am might be perfectly normal for a baby in one family, while sleeping from 6pm to 5am is the norm in another.
That said, early and late bedtimes can be useful for problem-solving certain sleep issues if you know which one to use. EITHER change could be necessary, but for totally different problems. The key is to figure out the root of your child’s sleep trouble first and then choose the strategy that best fits the problem.
Sleep is complicated and is driven by two mechanisms: sleep pressure and the circadian rhythm (read more about that here). When these two drives are in synch, your child will be rested throughout the day and will have a nightly sleep pattern that is consistent with what we describe on our age-by-stage sleep chart. When these two sleep drives aren’t in synch, problems ensue.
The build up of sleep pressure is intuitive: the longer you stay awake, the sleepier you become. The neurotransmitter adenosine builds up in your brain every minute that you stay awake (caffeine blocks adenosine, which is what makes you feel awake when you drink it). In young children, sleep pressure is the dominant force behind naps. Whatever age your child is, there is a limit to the number of continuous hours he or she can be awake (see our nap 101 series for more information on this). If your baby is a newborn, then he or she can probably only stay awake for 1-2 hours at a time. If your baby is 6 months old, then he or she may be able to tolerate 2-4 hours awake at a time, depending on the time of day. If your baby is 18 months old, then he or she can probably stay awake for 5-6 hours at a time during the day. When your baby goes beyond these limits of wakefulness, he or she will experience acute sleep deprivation. This means that he or she will be beyond her comfortable limit of sleep pressure, and thus likely harder to settle when you do put her down for a nap or bedtime.
Unfortunately, sleep pressure can also accumulate over a series of days. This is the build-up of chronic sleep debt that comes when your baby needs (for example) 14 hours of total sleep in a day but only gets 12-13 each day. Over time, that chronic sleep debt will obscure your ability to detect any sort of pattern in your child’s sleep. Chronic sleep debt is a stressor that can increase night waking and lead to waking too early from naps.
Now let’s sidestep to the circadian rhythm for a moment.
Unlike sleep pressure, the circadian rhythm is not at all intuitive. It is your central biological clock and it plays a role in a LOT more than sleep (production of many hormones, urine output, etc.), but it is the dominant force behind the consolidation of nighttime sleep. The circadian rhythm also controls the drive to be awake. Let us say that again: the circadian rhythm controls the time you sleep and the time you are awake. The circadian rhythm synchronizes biological function based on your exposure to light and darkness (this is why we’re so emphatic about telling you to keep your child’s room dark!). When your child has a regular schedule, the strongest drive to be awake happens right before your child’s biological bedtime and another drive to be awake happens in the morning at your child’s wake time. The consequence of this is that if your child doesn’t get the right distribution of naps during the day, you can end up with a situation where she’s obviously tired, but unable to sleep when you try to put her down early. This can lead to frequent waking at the beginning of the night. It can also sometimes lead to a “split night” where there is one really long stretch of awake time in the middle of the night (read more about split nights here).
Knowing how those two sleep drives work and how they work together will help you problem solve. Here’s how it breaks down:
When should you offer your child an EARLY bedtime?
1. When your child is acutely sleep deprived (e.g., an “off” nap day). If your child normally gets enough sleep, but misses a nap on occasion or has a gap of wakefulness that is too long, then you’ll want to offer a somewhat early bedtime to compensate. For example, if your child normally takes three naps and goes to bed at 7:30pm, then you might put your baby to bed at 7:00pm on a day when he or she skips the third nap. This is also a way to compensate for a poor napping day at daycare.
2. When your child is chronically sleep deprived (never gets enough sleep). If your child is chronically sleep deprived, then your first priority should be catching him or her up on sleep in order to break the negative pattern that arises from chronic sleep deprivation. An easy way to do this is through offering your child an extremely early bedtime for a few days in a row to catch up on sleep. You’ve probably observed this yourself, but babies and toddlers don’t sleep in later when they are sleep deprived, and increasing nap duration can be a challenge. However, a chronically sleep-deprived child will be able to fall asleep one or even two hours before bedtime and will be able to sleep until morning (if your child normally wakes at night, he or she will probably still have some night waking). Although there is a very strong drive to be awake right before bedtime, an extremely sleep-deprived child can sleep through that and keep sleeping through morning. This is because that build up of chronic sleep pressure is so high that the “catch-up” sleep just gets tacked on to the night, and then the circadian rhythm takes over to keep your child sleeping from the time of her biological bedtime until morning. If your child is chronically sleep-deprived to a significant degree, then you might offer bedtime at 5:30pm for a few days in a row to catch up, instead of the usual 7:00pm.
Sometimes parents report chronic daytime sleep debt due to a childcare environment they cannot control. In these cases (extremely poor daytime napping 5 days per week) we suggest an ultra early bedtime (1-2 hours early, as described above) two days per week to help prevent an accumulation of too much sleep debt throughout the week.
Note: You don’t want to offer the super-early bedtime permanently, because that will start to pull the circadian drive to sleep earlier, and suddenly your child will be waking a few hours earlier for the day.
Note: Notice that chronic sleep deprivation (example 2) is different from acute sleep deprivation (example 1). One day of a skipped 30-minute nap does not lead to a bedtime that is 1.5–2 hours earlier!
3. When your child is waking early in the morning but is still tired (can easily go back to sleep with help). In some cases, offering a moderately early bedtime (20-40 minutes earlier) for just a few days will stabilize your child’s pattern and will actually lead to him or her sleeping in later than before. This is not true for every child, but if the only sleep issue that your child is experiencing is a small amount of chronic sleep debt, this type of early bedtime can help offset that sleep debt and reset your child’s ability to sleep later in the morning.
If your child is chronically sleep deprived and doesn’t know how to fall asleep independently, then you may also need to do some sleep intervention. First help your child catch up on sleep; then you can teach him/her how to fall asleep on their own. Remember, there are many layers to fixing sleep issues, and it's rare that making just one change will solve everything. If you need help sorting out your child's sleep problem, contact us to schedule a personalized consultation.
When should you offer your child a LATER bedtime?
1. When day/night sleep is out of balance and your child is spending too long in bed. For families who embrace an early-bedtime philosophy, this can become a very common problem as their baby grows and matures. It’s also common if your child is getting very little sleep during the day, resulting in him or her being in bed at night much longer than the averages on our sleep chart. In this case you’ll want to focus on getting your child rested during the day and move bedtime later in order to shorten the time in bed overnight. When the balance and distribution of sleep is off in this way, you end up with long stretches of wakefulness in the middle of the night that no amount of sleep training will fix (because it’s really a biological problem, not because your child doesn’t know how to fall asleep). You can also have this type of “split night” if you try to make your child stay in bed for 12 hours each night, but he or she only needs 11 hours of sleep. In this case he/she will be rested but will be awake for an hour at some point during the night.
2. When your child is waking (too) early and is wide awake in the morning. If your child wakes for the day too early and is clearly ready to go (e.g., wakes every day at 5:00am and is happy and rested) then it’s likely that his or her drive to be awake is happening too early and he/she doesn’t have the capacity to sleep later. In this situation you’ll need to shift her circadian rhythm later (just like what would happen with jet lag or daylight savings time). You can do this by offering a later bedtime and controlling your child’s exposure to light and darkness. Provide nice, bright light in the evening up until about 15–30 minutes before bedtime, then dim lights, and finally keep things very dark from bedtime until the desired morning wake time. Since it takes a while for the circadian rhythm to adjust to change, you shouldn’t expect to see a later wake time until your child has had at least three nights of the later bedtime (that’s the "lag" in jet lag). See our blog on fall daylight savings time for step-by-step instructions about how to shift a schedule later.
3. When your child’s sleep needs have changed. Some parents convince themselves that an early bedtime is required long after their child's nighttime sleep requirements decrease. This leads to asking your child to sleep at a time when he or she is just not able to sleep. This can happen with babies, but it is most common in toddlers. The circadian drive to sleep naturally shifts later between age 1 and age 3. If you have a toddler whose drive to sleep is happening later than his or her bedtime (see our bedtime battles blog for more info), then you will end up with all kinds of trouble. To fix this, first figure out the average time when your child has fallen asleep over the course of a week. This is his or her biological bedtime. Once you figure this out, put your child down at his or her biological bedtime, so that he/she is ready for sleep when you are asking him/her to sleep. You can then gradually move bedtime earlier in 15-20 minute increments until you are putting your child down at a socially acceptable time.
Here’s where it gets tricky…
Sometimes you might need a plan that incorporates a super-early bedtime for a few days, followed by a late bedtime and sleep intervention! This is what we call the art to the science. Science tells us a lot, but we need to consider the complexities of sleep at each age as well as an individual baby’s experiences in order to problem solve successfully. If you are struggling with how to put all of the pieces together, consider booking a consultation with us, and we’ll help you figure it all out.