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What Everyone Should Know About Sleep Debt

Sleep Debt Man With Coffee (679)

How much sleep do you need to do your best work?

Is it 6 hours? 7 hours? 8 hours? Or more?

Personally, I’ve never taken sleep that seriously. Most of the time, I’ve considered a good nights sleep a luxury. I used to put off sleeping, pushing through deadlines by consuming caffeine and sugar. Sacrificing sleep wasn’t even a question – it was a given!

But at what cost? Was I doing my best work?

What Is Sleep Debt?

A few years ago I was in the middle of a software rollout to multiple hospitals. I worked crazy hours and used coffee and chocolate to survive.

But I accumulated what sleep scientists call “sleep debt”.

Sleep debt is defined as “the cumulative hours of sleep loss compared to an individuals need for sleep.”[1]

Researchers at the Washington State and Pennsylvania Universities conducted a range of sleep experiments on healthy adults. They wanted to see what would happen to research participants if they lost just a bit of sleep, each night, for 2 weeks.[2]

Here’s what they found: sleep debt massively reduced brain performance.

In one group whose sleep was restricted to 6 hours a night for 2 weeks, cognitive performance declined to the equivalent of staying up for 48 hours straight.

Whoa. That’s terrible!

When I read this it made me stop and think. I’ve often gone a week or two on just 6 hours of sleep a night. Sure I felt a bit tired and even grumpy but I thought I was functioning well.

But maybe I wasn’t?

Trading Sleep For More Work Is Dumb

When I reflected on what I had done in the past, it dawned on me that I had traded sleep in an attempt to get more things done.

Yet it often proved to be counter-productive.

During those times when I traded sleep for several consecutive nights, I seemed to take longer to finish tasks and had lower quality results.

Here’s what Gregory Belenky from the Washington State University Sleep and Performance Research Centre[3] has to say about sleep debt and performance:

“You don’t see it the first day. But you do in five to seven days. Unless you’re doing work that doesn’t require much thought, you are trading time awake at the expense of performance.”

In my experience there’s a lot of pressure to sleep less and work more. Burning the candle at both ends is often seen as a commitment to your work. Funny thing is, this badge of honour is exactly what prevents you and I from doing our best work.

It might work occasionally to pull a late night to get something extra done, but long term it’s not a smart way to work. You lose efficiency, focus and make more mistakes.

Are You The Best Judge?

Here’s the intriguing part of sleep debt.

Sleep deprived workers are terrible judges of their own altered performance. They lose the ability to recognise how poorly they are performing day to day.

In the previously mentioned study researchers found that participants’ self-reported ratings of sleepiness did not increase after day 2. Even after 14 days of accumulated sleep debt, people reported feeling only slightly sleepy, even though their performance had dropped to the same level as the group without sleep for 48 hours.

Sun up. Sun down. Sun up. Sun down. That’s 2 days in a row.

By now you’re practically sleepwalking… and you don’t even know it.

So How Much Sleep Do You Need?

If 6 hours isn’t enough for most people, then what is?

Short answer:

Most researchers agree that 95% of adults need a minimum of 7 – 7.5 hours sleep before they start accumulating sleep debt.

Long answer:

It differs.

In the Van Dongen et al. study, participants that slept for 8 hours a night over 2 weeks performed best. In another study lead by Gregory Belenky, participants that slept for 9 hours a night performed similar to Van Dongen’s 8 hour group.

In Belenky’s study, a group of participants were restricted to 7 hours of sleep. These people had mild but measurable declining brain performance after a few days. Other studies have targeted individual factors (eg. age, gender or pregnancy) that may affect how much sleep you really need[4]

95% of adults need a minimum of 7-7.5 hours sleep a night

Bottom line: Anything less than 7 hours a night is a gamble and over time, is likely to result in sleep debt.

Paying Back Your Sleep Debt

Here’s some good news if you need to punch through a deadline and sacrifice some shut-eye.

You can make up for lost sleep on a late nighter in the following 24 hour sleep cycle using naps and additional hours of sleep the following night.

Take a nap in the afternoon after a night of sleep loss and research shows that you decrease sleepiness and improve performance.[5] Winston Churchill certainly thought so. He wrote that his afternoon nap between 1.5-2 hours was essential for helping him cope throughout the war.

But remember — sleep debt is cumulative. Sacrificing more hours each night means adding to your debt.

Feeling Sleepy?

Here are some take-aways…

  • aim for at least 7 hours of sleep a night
  • remember that sleep debt accumulates over days and weeks
  • occasional late nighters are ok – just get more sleep the next day/night
  • you and I suck at judging whether sleep debt is lowering our own performance.

What’s one thing you might do this week to start paying back your sleep debt?

Need help to improve productivity during your waking hours? Check out our Training and eLearning pages.


Footnotes    (↵ returns to text)

  1. Van Dongen et al., (2003). Sleep debt: theoretical and empirical issues. Sleep and Biological Rhythms. 1:5–13.
  2. Van Dongen, HPA., et al (2003). The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation. Sleep. 26:117-129.
  3. New York Times. How Little Sleep Can You Get Away With?. April, 2011. Weblink:
  4. Medina, J. (2008). Brain Rules 12 principles for surviving and thriving at work, home and school. Pear Press, Seattle, 151-168.
  5. Vgontzas, A., et al (2006). Daytime napping after a night of sleep loss decreases sleepiness, improves performance, and causes beneficial changes in cortisol and interleukin-6 secretion. American Journal of Physiology, Endocrinology and Metabolism. 292:253-261.

One comment

  1. Good article – if only naps were more accepted in the workplace! Does this mean Sleepy was the most productive of the 7 Dwarfs or was he just overworked?

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