Recently a study came out in Child Development looking at sleep consolidation in toddlerhood and the potential effects on cognition. I have summarized the results elsewhere, but suffice it to say there were no effects of sleep consolidation on cognition, but there were between subject effects of socio-economic status on cognitions. (Take-home: don’t worry if your toddler wakes at night – they aren’t getting dumber because of it.)
What struck me though about this study was that the sample was large enough and the sleep data complete enough to give us some pretty good information on the development of sleep in the toddler years, something that can be lacking. The study examined children recruited at 30 months (2.5 years) and followed them for one year, gathering data at 30, 36, and 42 months of age. The sleep data was gathered using actigraphy to avoid parental bias or mistakes and consisted of two weeks’ data at each time point to allow for averaging of the nights. The number of children with sleep data at each time point was N=420, 324, and 276 for 30, 36, and 42 months, respectively. Considering there’s actigraphy involved, this is an excellent size sample for normative data.
Now I should say that most people actually expect their toddlers to be sleeping through the night and immediately panic when their child wakes. Some professionals acknowledge waking is normative, but if the child needs assistance, it becomes problematic. I admit I’m never quite sure why needing help is a problem as there are lots of things going on for toddlers that can make wakings more common and harder to handle on their own.
So what is normal? According to the actigraphy on this group of predominantly-Caucasian children (which does matter, but it is what it is):
- Toddlers wake frequently. The average number of wakings that were longer than 5 minutes after sleep onset went from 4.72 at 30 months down to 4.06 at 42 months. Yes, that’s right, at 3.5, kids were still waking an average of 4 times per night. Now, they were not waking their parents for all of these, but as evidenced by needing to be longer than 5 minutes to be counted, they weren’t super brief either.
- Toddlers can be awake for a while. The average duration of the longest awakening was 31.18 minutes at 30 months, 25.77 minutes at 36 months, and 23.89 minutes at 42 months. So it was quite common for toddlers to have a longer awakening in the middle of the night. How many of these kids got their parents during this time, we don’t know, but if you’re co-sleeping or your child wants to see you, chances are you’re being awoken.
- Later bedtimes are normal. Despite earlier bedtimes of around 8:50pm at all three ages, the average time of actual sleep onset was around 9:30pm at all three ages. This is something I have spoken at length to families about as later bedtimes actually are quite normative in the infancy and toddler years and is reflected in average bedtimes in other cultures. So no, you’re not a bad parent for having a bedtime that’s more in line with your child’s biology.
- They sleep less than we think. The average amount of time in bed was around 10.4 hours at all three ages, but the actual time asleep was 8.18 hours at 30 months, 8.43 hours at 36 months, and 8.51 hours at 42 months. The increase over time likely reflects a normal decrease in day sleep that tends to happen in that 2.5 to 3.5 year range. Now this includes the long time to fall asleep that most of these kids had so the time awake overnight isn’t quite this bad, but the fact that the kids are sleeping far less than we think is worthy of discussion. Too often we worry about kids needing things like 11-14 hours when in reality they are getting less than this and seem to be functioning just fine.
What do we take from this? Toddlers wake. Depending on many other factors such as whether or not you’re still breastfeeding or you co-sleep or your child just likes you a lot, they may or may not wake you during these periods. These wakings will decrease in time and you can rest assured that your wakeful toddler is likely very normal, thank you very much. If you are worried, take a look at your toddler’s daytime behaviour and if all seems well, I wouldn’t worry about those times they just want to sing you the alphabet at 3am.
 Hoyniak CP, Bates JE, Staples AD, Rudasill KM, Molfese DL, Molfese VJ. Child sleep and socioeconomic context in the development of cognitive abilities in early childhood. Child Development 2019; 90: 1718-1737.