The 40 Minute Sleep Intruder

Ever been through this with your baby? You put her down for a nap, or maybe it’s bedtime. She goes down to sleep pretty nicely, without much fuss. You sit down to relax and unwind a bit… and just 40 minutes later, she’s up and she’s had it.

Waking up and crying after 40 minutes of sleep has a special name: The 40 Minute Sleep Intruder.

There’s an explanation behind this phenomenon. The average sleep cycle of your baby for the first 9 months of life is…45 minutes. This means that approximately every 45 minutes, your baby experiences partial arousal, where she is in a very, very light stage of sleep. Imagine hovering in between awake and asleep – not quite awake, but not fully asleep – that’s where she’s at. If your baby is comfortable at this point and her environment has stayed the same, she will likely fall back asleep and being a new 45-minute cycle of sleep. But any change in temperature, noise, or discomfort will rouse your baby completely and bring her to a fully awakened state.

So how do you explain 40-minute wakings if nothing has changed in your baby’s room since she fell asleep? You know she’s fed, her room is dark, quiet and cool and her diaper is clean. That leaves you with only one other option, the main culprit of the 40 Minute Sleep Intruder:


One of the most wide-spread myths of baby sleep is that the more tired your baby is during the day, the better she will sleep at night. This is NOT TRUE! In fact, the opposite is true.

A baby that gets enough sleep during the day will sleep better at night, and a baby who is not napping at the right times and for the right duration will wake more frequently at night.

Sleep begets sleep. Lack of sleep begets…lack of sleep.

How to solve the 40 Minute Intruder

  1. Watch your baby’s wake windows. It’s very important to put your baby down for naps at the right time, according to her age. If you keep a baby awake for longer than she’s biologically designed, you’ll end up with a wired and tired fusspot who won’t sleep well at night.
  2. Move bedtime earlier. It won’t make her wake earlier in the morning. If your baby like this at night, chances are she needs more sleep. Moving bedtime back by 30 minutes for a couple of weeks should help.
  3. Let your baby try to fall back asleep on her own. Don’t try this one in a vacuum, though – make sure to adjust the previous two elements as well before trying this. It’s important to realize that your baby often does need some space to figure things out on her own. Running into her every time she starts to fuss will only add to the problem.

Be on top of those wake windows and make sure to move bedtime earlier. Things usually improve by 6-8 months even if you don’t do any of the steps listed above. If your baby is older than 8 months and is still struggling after you’ve implemented the steps above, you’re probably left with a sleep dependency. 

By | 2019-09-04T14:40:20-04:00 September 4th, 2019|Categories: Sleep Troubles|0 Comments

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