Why you’re so tired even when you’ve "slept" 7 hours ?
Ever feel like you’ve been awake all night, even though the clock says you should be rested? It turns out there is a scientific reason why new parents feel near-universal fatigue during this time.
At Wyndell, we have searched the literature for answers and are bringing these right to your mail box. We’ve been diving deep into a 2013 review from The Open Sleep Journal by Montgomery-Downes et al., which looked at years of data on how new parents actually sleep. The study was divided into different categories and we will discuss here parts that we at Wyndell found of particular interest as they relate to sleep in new mothers, but feel free to read the full paper for more details!
In a first part, the authors focused on the notion of sleep fragmentation. While you might feel completely sleep-deprived, research shows that many new mothers actually average between 7.2 and 7.8 hours of total sleep per night. The real culprit isn't necessarily the amount of sleep, but sleep fragmentation.
The "Fragmentation" Factor
Your sleep is being frequently interrupted, which breaks your "sleep architecture" and prevents you from getting the full neurocognitive benefits of a solid night's rest. This fragmentation causes the same levels of daytime sleepiness and mood disturbances as having no sleep at all.
This happens because babies follow a polyphasic sleep pattern. Their sleep cycles last only 50–60 minutes, while yours are designed for 90-minute stretches. Because your sleep is so broken up, you likely overestimate how much time you spend awake during the night because your brain never gets to settle into a deep, efficient rhythm.
The Mind-Body Connection: Your Perception Matters
The authors then explored a concept we found particularly powerful: subjective sleep disturbance. This is the scientific way of saying that how you feel about your sleep can be just as impactful as the sleep itself. It turns out that your subjective sleep quality—your personal "gut feeling" about how you rested—is actually a better predictor of your daytime sleepiness and fatigue than the objective number of hours you slept.
The "Overestimation" Trap
Interestingly, the study found that new mothers often overestimate how long they were awake during the night. Because your sleep is so fragmented by your baby’s needs, your brain doesn't get the chance to settle into a deep rhythm, making it feel like you were awake much longer than you actually were. This, however, does not mean you are not tired, it just means that the reasons for this fatigue does not necessarily come from lack of sleep but rather from sleep fragmentation.
So, how can we use this? While every mother’s journey is unique, reading this paper brought up three things to reflect on:
- Since our minds tend to overestimate how long we are awake during the night, it can be incredibly validating to see the real numbers. If you're curious, try briefly jotting down your actual sleep and wake times for just one night. You might find you're getting more total rest than your brain is giving you credit for, which can actually help lower your subjective sleep disturbance.
- Our minds and bodies are deeply connected. In fact, research shows that "not being able to get a break" is one of the strongest factors linked to a lower mood during this period. Defining even a small window of time to do something you truly love isn't just a luxury—it’s a biological strategy to help you recharge and manage the fatigue that comes with fragmented sleep.
- It’s easy to feel like you’re doing something wrong when you’re this tired. But the experts want you to know that this is a normative developmental period, not a permanent sleep disorder. You are simply in a season of "negotiated behavior," where you are skillfully matching your rest to your baby’s needs.
Simply acknowledging that this stage is expected and that your body is working hard to adapt can be the first step in reclaiming your energy.
Let us know what you think and what your strategies are in the comments!