I've returned to work, but I can't go back to the 'old me'—the culprit is accumulated sleep debt

“I used to be able to do so much more before I had my baby.”

It’s been a few months since I returned to work. I’m managing to get my job done, somehow. But something feels off.

Words don’t come to me quickly in meetings. It takes me longer than before to put documents together. I find myself saying, “Wait, what was that word again?” more often. Ideas don’t flow. My judgment feels fuzzy.

“Have I become stupid?”

Have you ever felt depressed thinking that?

That’s not it. You haven’t become stupid. Your brain just hasn’t finished paying off its debt yet.

The name of that debt is sleep debt. It quietly piled up during pregnancy, after childbirth, and throughout your maternity leave, and it remains deep within your body even after returning to work. That is the true identity of why you 'can't go back to the old you.'

◎ What is sleep debt?—Debt accumulates quietly

Sleep debt is a state where chronic sleep deprivation has accumulated.

If you are short one hour of sleep a day, you accumulate seven hours of 'debt' in a week. The problem is that this debt is difficult to notice.

In a study by Dr. Van Dongen and colleagues at the University of Pennsylvania (Van Dongen et al., 2003), a group that slept for six hours for two weeks saw their cognitive function decline to the same level as someone who had stayed awake for two full days, yet the participants themselves felt, 'I’m a little sleepy, but I’m fine.'

The brain cannot notice its own decline in function. Because it gets used to it.

The scariest part of sleep debt is that it becomes 'this is my normal' rather than 'I’ve been feeling off lately.'

◎ The true nature of the 'invisible debt' accumulated during pregnancy and maternity leave

Those who have experienced it know just how fragmented sleep is after childbirth.

Newborns need to be fed every two to three hours. The longest you can sleep at a stretch is three hours. Non-REM sleep (deep sleep), which determines the quality of your rest, is only achieved after sleeping for 90 minutes or more continuously. In other words, nights where you cannot sleep deeply continue for months.

Even when the child gets a little older, there is no end to the things that fragment your sleep—night crying, fevers, and tossing and turning while co-sleeping.

Dr. Walker (Walker, 2017) states that not only the 'quantity' of sleep but also 'uninterrupted sleep' is essential for the recovery of cognitive function. Even if you sleep for eight hours, if it is broken up, the restorative effect on the brain is significantly reduced.

The one to two years from childbirth through maternity leave. The sleep debt accumulated during this period does not automatically disappear just because you returned to work. You need to properly 'repay' the accumulated debt.

◎ The neuroscience behind why performance doesn't return even after returning to work

When sleep debt becomes chronic, the function of the prefrontal cortex remains impaired.

The prefrontal cortex is the "brain's command center" responsible for logical thinking, verbalization, judgment, and idea generation. When this area is chronically exhausted, you experience a persistent state of "not being able to find the right words," "not being able to organize thoughts," and "taking longer to do things that used to be easy."

Furthermore, the hippocampus, the center of memory, is also affected. During sleep, the hippocampus organizes and consolidates information from the day, but in a state of sleep debt, this "memory transfer" does not work well. If you find that things you learned at work aren't in your head the next day, or you keep checking the same things over and over—this may be due to hippocampal exhaustion.

"I could do more before I had my baby" is not just your imagination. Your pre-pregnancy brain and your current brain, burdened with sleep debt, are literally in "different states."

Everyone is the manager of their own "body." Just knowing this allows you to shift from self-denial, thinking "I've become stupid," to an objective perspective: "My brain is still in the process of recovering."

◎ "The old me" hasn't disappeared—it returns when you pay off the debt

This is the most important thing I want to convey.

The brain has "plasticity." A brain that has accumulated sleep debt can also recover its function by accumulating high-quality sleep.

Research by Banks & Dinges (2007) shows that after sleep restriction, taking sufficient recovery sleep allows most cognitive functions to return to their original levels.

"The old you" has not disappeared. It is just sleeping beneath the sleep debt.

If you fix your sleep, it will come back. Slowly, but surely.

Goal first! Method second!—Set the goal of "myself having regained my pre-pregnancy performance" first, and then fix your sleep as a means to achieve it. If you think in this order, you will see what you need to do starting tonight.

◎ What changed 3 months after returning to work with a heavy head

Let me tell you the story of a mother in her 30s.

Six months after returning to work, she told me, "I'm scared because I feel like a different person from who I used to be." She couldn't voice opinions in meetings. The speed at which she wrote project proposals was less than half of what it was before she had her baby. She had even started to think, "Maybe I'm not cut out for this job."

The only thing we reviewed together was her sleep rhythm. She fixed her wake-up time, stopped using her smartphone before bed, and decided on a time to dim the lights. That was all.

Two months later, she told me, 'I feel like my head is a bit clearer.' Three months later, she shared with a smile that for the first time in a while, she was able to raise her hand in a meeting. She said, 'Oh, I realized I was still here.'

The old me hadn't disappeared. She was just sleeping.

◎ Summary

I will summarize what I have shared today into three points.

・Sleep debt is hard to notice. The scariest part is that it becomes 'my normal'.
・Fragmented sleep from postpartum through maternity leave is an 'invisible debt' that continues to linger in the brain after returning to work.
・The brain has plasticity. When you regulate your sleep, the prefrontal cortex and hippocampus recover, and your performance returns.

Sleep is a skill and a tool. When you think, 'I want to go back to my old self,' the first thing you should work on is improving the quality of your sleep.

Time flows from the future. The version of you that has regained your pre-pregnancy performance is already beginning in tonight's sleep.

——Have a pleasant day again today

■ References

・Van Dongen, H. P. A., et al. (2003). The cumulative cost of additional wakefulness. Sleep, 26(2), 117-126.
・Walker, M. (2017). Why We Sleep: Unlocking the Power of Sleep and Dreams. Scribner.
・Banks, S., & Dinges, D. F. (2007). Behavioral and physiological consequences of sleep restriction. Journal of Clinical Sleep Medicine, 3(5), 519-528.