The “Split” Night: Why some babies are awake for hours in the middle of the night, and how to change

The “Split” Night: Why some babies are awake for hours in the middle of the night, and how to change

(Revised and updated from an earlier version.)

There may be a time when you find yourself up in the middle of the night for hours with your baby who just won’t sleep! A split night is easily distinguished from other situations where your baby may be up during the night: it usually only involves one long waking, it happens every night or every few nights, most babies will be in a good mood during the long awake stretch, and no amount of comforting, nursing, soothing or sleep training will get your baby back to sleep quickly. A split night is largely a biological issue, arising from a dissociation between the sleep drives. Many babies will actively try to sleep by changing position, finger sucking, or snuggling a lovey. The issue for these babies is not that they don't know how to sleep, but that they can't fall asleep. As a result, sleep training will not fix a split night issue. If it sounds like your baby is having a split night, read on!


The Science

There is a maximum number of hours that a child can sleep at night (see our common age by stage sleep chart). Consolidated nighttime sleep is driven by two factors: (1) the circadian rhythm enabling bed and wake time to happen at appropriate times, and (2) sleep pressure arising from staying awake for an appropriate amount of time during the day. When things are going well, your baby will build sleep pressure during the evening and go to sleep at a regular time, and will sleep through the night. As sleep pressure dissipates with night sleep, the circadian rhythm will take over and keep your baby asleep for his/her maximum sleep duration and wake up at a regular time. That pattern will be fairly stable within about a 30-minute range on either side. When a split night happens, the sleep pressure drive separates from the circadian rhythm. This means that your baby may sleep for 8-9 hours and wake up feeling pretty refreshed and ready to go … at 2 am! Your baby will be up for a while and build up a bit more sleep pressure, and then, as the circadian drive kicks back in, your baby will sleep for a few more hours until morning. This pattern usually sticks, leaving your baby with hours of happy waking in the middle of every night. If you look at this graphically (the reason we love when parents track sleep!), the problem is usually that your baby has gotten into a pattern of having too many hours in bed every night and is not able to fill that time with sleep.


Need More Help?

We offer several options for optimizing your child's sleep:

SLEEP TRAINING CLASS (for well babies 6-15 months)

PHONE CONSULTATIONS (with one of our sleep experts)

THE SECRET TO NAPS (downloadable e-book)


There are two primary causes of a split night:

1. Split Night Caused by Poor Napping and Extra-Early Bedtimes

This is the most common cause of split night, and it is almost always remedied by schedule changes. There may be times when your baby can sleep more than his or her typical sleep duration. For example, if your baby has had a really terrible nap day, then you might put him/her down early for the night in order to help her catch up on sleep. This is usually a good decision and will lead to a longer-than-usual night of sleep with morning wake time remaining consistent. The reason that an occasional extra-early bedtime works is because of the two sleep drives (more on the basics behind sleep drives). When your baby accumulates a sleep debt (over-tiredness, a.k.a. high sleep pressure), he or she can go to sleep early but will sleep until his/her normal wake time. This is because the circadian rhythm controls wake time, and it takes a few days to change the circadian bed/wake time. The problem is that, after a few days of an early bedtime, one of two things will happen: either (1) your baby will start to wake up earlier, with a normal duration of sleep or (2) your baby will develop a “split” night, during which he or she stays in bed for more hours than he/she is capable of sleeping and thus has a long span of time awake in the middle of the night. This is a very common trouble spot for parents who subscribe to the early-bedtime-solves-all-problems philosophy.

How does this happen?

It’s so easy to get into a bad cycle. For example, your baby might have a poor nap day and be exhausted an hour earlier than normal. In this case, you might put your baby down an hour early to help him or her catch up on sleep, and he/she will likely sleep until a normal wake time. Then, the next day he/she might have another bad nap day, and you might put him/her down early again. Then, another bad nap day and another early bedtime, but by around that third day, your baby's sleep pressure may start to dissipate in the middle of the night, and he or she might be happy, refreshed, and ready to go at 2:00 am. You might try to rock, comfort, or nurse your baby to get him/her to sleep, but since he or she isn't sleepy, he/she probably won’t sleep for at least an hour. After an hour or so, your baby will feel sleepy again and fall asleep. In the morning you will probably let him or her sleep until normal wake time, or you might even let him/her sleep-in, thinking that you should allow extra sleep in order to make up for that time awake in the middle of the night. If the poor naps, early bedtim