Sleep Debt Accumulates Quickly

Even a small sleep debt requires a surprisingly large payback.

I’m always on alert for new sleep studies. I find that sleep is a major roadblock in nutrition and fitness. I recently discussed how sleep can change hunger levels, but it can also put us at risk for metabolic, immune, digestive, and memory issues among others.

In a report that just came out1, researchers measured potential sleep debt in young men. The subjects were able to sleep up to 12 hours for over a week, followed by one night of being awake, and another night of sleeping up to 12 hours. Not a bad study to sign up for.

The scientists were looking to measure how much the subjects normally sleep versus how much they could sleep if uninterrupted by life. Using this difference, say 7 hours of sleep normally versus 9 uninterrupted, we can predict how much sleep debt you may be in. Since individuals vary in how much sleep is required, this could be a rough method to determine the magic number for sleep on an personal basis. I use the range of 7 to 9 hours, but being able to be specific would be ideal.

The researchers found that it takes around 4 days of sleeping-in to bring you back to normalized levels after even 1 hour of sleep debt (or not sleeping to optimal level). It was a decent study because they also tracked blood markers. After catching up on sleep, cortisol was slightly lowered, glucose metabolism slightly improved, and thyroid function was slightly better. Small improvements but it was a short duration study using only young males. It gives hope for future studies.

Measure your sleep debt to calculate how much sleeping-in you’ll need to fix it.

Using a laboratory like the researchers did is an expensive way to track sleep. A takeaway here is that we can estimate your optimal sleep levels using sleeping-in or a vacation as data. Sleeping in one day isn’t a great measure, because you can be in such a big sleep debt that you will overcompensate. If there is a time in your life (hopefully a vacation) that you can sleep as much as you want for more than 3 or 4 days, this will work. After 4 days your sleep should normalize, so if you slept 12 hours the first night, 9 the second, 8.5 the third, and 8.5 the fourth, you will know that 8.5 hours of sleep is optimal. Anything you get under that number is sleep debt.

The researchers also controlled for food, alcohol, and general lifestyle factors. Outside of a laboratory, we don’t realistically have that luxury; nonetheless we can gather some data on ourselves. It’s a big challenge to get enough sleep in this world. However, we can’t cheat our biology. Go to bed!

1. Kitamura, Shingo, Yasuko Katayose, Kyoko Nakazaki, Yuki Motomura, Kentaro Oba, Ruri Katsunuma, Yuri Terasawa, Minori Enomoto, Yoshiya Moriguchi, Akiko Hida, and Kazuo Mishima. “Estimating Individual Optimal Sleep Duration and Potential Sleep Debt .” Scientific Reports 6 (2016): 35812. Accessed October 27, 2016. doi:10.1038/srep35812.

Be the smartest person in your gym

Everything you need to know about strength in in your inbox.