Can You Make Up Your Sleep Debt?

A night of getting less sleep than you need doesn't get written off - it accumulates in what is known as sleep debt. See if you might be racking up sleep debt and what you can do about it.

By Sheryl Grassie

Expert Insights from Dr. Brooke Dulka, a medical writer and neuroscientist who received her Ph.D. in biological psychology from the University of Tennessee, and she is currently a postdoctoral researcher at the University of Wisconsin-Milwaukee where she studies the neurobiology of memory.


We all know how spending more than we have turns into debt, but did you realize that sleeping less that you need becomes a kind of debt too? Sleep debt is the result of not enough sleep over a period of time and is connected with numerous health complaints. Read on to learn more about whether or not you might be racking up a debt for sleep.

What is Sleep Debt?

Simply put, sleep debt is the sum of too little sleep over time; the accumulated difference between what you need to sleep each night and what you actually sleep each night. Since the recommended amount for adults is between 7-9 hours per night, anything less than 7 hours is considered insufficient or “short sleep duration,” and this difference accumulates as part of your sleep debt.

For example, if you only sleep 6.5 hours a night, you are short at least 30 minutes, and possibly more, per sleep cycle. In reality, many people need 8 or 9 hours, so anything less than what you need becomes part of your debt. Over time, this can add up to a substantial number, and over time this mounting debt can have serious consequences to physical and mental health.

Negative Effects of Accumulating Sleep Debt

“Not getting enough sleep can lead to numerous other health problems. Most people need anywhere from 7 to 9 hours of sleep each night,” says Dr. Dulka.

Sleep debt tends to accumulate: about two weeks of less than 6 hours sleep a night reduces alertness and performance to a level equivalent to a full 24 hours of sleep deprivation; a week of only four hours sleep a night is equivalent to 2-3 days without any sleep; etc. Daytime performance continues to worsen as the sleep debt builds up, although it is still not clear up to what point.

Studies show that the effects of sleep deprivation have a definite correlative effect with a number of short-term and long-term health conditions. Research illustrates a connection to weight gain, obesity, diabetes, heart disease, and stroke. Lack of sleep affects cognitive clarity, depression, and may trigger manic episodes in individuals with bipolar disorder. It can make you accident-prone and lower immune function.

Lack of sleep may be the hidden cause behind many, or even most, of the “human error” that causes so many accidents each year. The sleep debt accumulated by shift workers makes them particularly vulnerable to accidents and injuries, and it is no coincidence that many high-profile industrial and transportation accidents (e.g. Exxon Valdez, Chernobyl, Bhopal, Three Mile Island, etc) occurred at night. 

The risk of accidents in general is estimated to be about 30% higher on night shifts than on day shifts, with the risk increasing with the duration of the shift and the number of consecutive night shifts worked.

As most people will have experienced personally, even one hour of sleep a night less than the optimal amount takes a toll on our mood, energy and our ability to handle stress. “You may be getting insufficient sleep if you are yawning frequently throughout the day, experiencing memory lapses, or have less ability to concentrate and multitask,” says Dr. Dulka.

Insufficient sleep typically manifests itself in a whole array of physiological and behavioral effects including: 

  • Yawning
  • Reduced alertness
  • A diminished ability to concentrate and multitask
  • Memory lapses
  • Impaired reaction time and reflexes
  • Aching muscles and muscle fatigue
  • Dark circles or bags under the eyes
  • Increased blood pressure
  • Increased stress hormone levels
  • Irritable or aggressive behaviour
  • Confusion
  • Increased risk-taking and poor decision-making
  • Hallucinations

In the longer term, sleep debt has been associated with a whole host of serious and even potentially life-threatening conditions, including an increased risk of obesity, type II diabetes, fibromyalgia, psychosis, depression, bipolar disorder, stroke, heart attack, impaired immune function, and high blood pressure, among others. 

Types of Sleep Deprivation

There are two types of sleep deprivation described in the research, total sleep deprivation and partial sleep deprivation.

Total sleep deprivation is no sleep for at least 24 hours. It causes short-term issues like lowered cognitive function and poor reaction time, and can be corrected with a few good nights of sleep.

Partial sleep deprivation is sleeping less than needed on a regular basis and can be problematic even if only for a few days or weeks. It can result in sleep debt and long-term health concerns like those described above.

Correcting Sleep Debt

Not getting enough sleep on a regular basis? You are not alone. Current research shows that the average person only gets 6.8 hours of sleep a night. This is considerably less than a century ago when the average was 9 hours. Estimates are that at least one-third of the population does not get enough sleep.

“A lack of sleep can be caused by numerous things such as insomnia, sleep apnea, or looking at a screen too late into the evening,” says Dr. Dulka.

Causative factors point to hectic lifestyles, long work weeks, and lack of emphasis on self-care. Many of us wear our lack of sleep like a badge of honor, “I get by on only 5 hours.” Our culture supports getting things done over needed sleep and the concept of making up for lost sleep is just coming into vogue.

In order to tackle chronic sleep debt, you can do a little research. First, ascertain how much sleep you are getting currently. Then determine the amount you actually need. The difference between these two over time is your sleep debt. Next, try to comprehend the cause of your sleep deprivation. And lastly, make a plan for recompense, how will you repay the debt?

How Much Sleep Do You Need?

Answering this question might be easy for some and difficult for others. You might be able to say I sleep 6.5 hours every night without fail, whereas someone else might say they sleep a different amount every night. If you are a pretty consistent sleeper, you can easily assess your average amount of sleep and move on to the next step. If you have inconsistent sleep patterns, you can record the amount you get each night in a sleep journal over several weeks to determine an average.

The Right Amount of Sleep

Some sleep experts say that sleep has a larger natural variance than some may think. We do know that the amount of sleep an individual needs varies from person to person. Somewhere in the 7 to 9 hour range applies for most people, but there are exceptions. People with a physical job, professional athletes, young children, teens, and older adults all need different amounts.

The easiest way to assess what your sleep needs are, is to notice how you feel with different amounts. It may be that 8 hours is the perfect amount for you, and you feel refreshed and focused the next day. It may be that you need more or less, only your body can tell you. Once you have determined the amount that works for you, take a look at your long-term pattern of sleep to determine if you have a sleep debt and how much.

Calculating Sleep Debt          

Calculating sleep debt can be daunting, especially if you think about the need to pay it back. Before we tackle how much needs to be paid back, and how to do that, just get an estimate of how much sleep you are short.

Have you been sleeping an hour less than needed for years? An hour a day would be 365 hours short a year. Multiply that by how many years you have been short on sleep and you will have an idea of the size of your debt.

Some sleep researchers say it is unrealistic, and not even necessary, to pay back all the lost sleep from years and years. However, the amount of sleep debt you currently have may well correlate to present health conditions, and eradicating those conditions may be supported by adding in more sleep.

Causes for Lack of Sleep

Before you can rectify your sleep debt, you have to have an idea of what is causing it.

  • Are you awake in the middle of the night from sleep apnea?
  • Do you have insomnia and lay awake for hours before falling asleep?
  • Are you consistently awake too early?
  • Do you lack a good exercise routine?
  • Are you outside and exposed to enough sunlight?
  • Are you on a screen late into the evening?

There are lots of possible factors that might contribute to your lack of sleep. For some it is a cultural norm: We have too much to do, and too much to worry about, and it compromises our sleep. Gain an understanding of what is affecting your sleep so you can do something about it.

You can also consult a sleep specialist who might give you one of several tests like the Multiple Sleep Latency Test (MSLT) or the Epworth Sleepiness Scale (ESS) to determine more specifically what your sleep issues looks like.

Paying Back Sleep Debt

Once you have established how much sleep you need, the approximate size of your sleep debt, and what is causing your lack of sleep, you can make changes in order to get more sleep. Paying back your debt is as simple as getting more sleep, but you must find ways to do it.

Regular nighttime sleep can be improved with better sleep hygiene practices like a consistent bedtime.  You may want to start taking melatonin or adjust your bedtime to get an extra hour nightly. You might consider taking naps or sleeping in on the weekends.

You don’t need a plan to pay back years and years of sleep deprivation, just concentrate on more sleep going forward. Get 9 hours instead of 8 hours and see what positive changes it will make to your health.

Research on Sleep Debt

  • Up to 60% of Americans say they have driven while sleepy within the last year, and 37% admit to having actually fallen asleep at the wheel. [Source]
  • It has been estimated that 17 hours of sustained wakefulness (for example, from 7am until 12 midnight) leads to a decrease in performance equivalent to a blood alcohol level of 0.05% (two glasses of wine), the legal drink driving limit in many countries. [Source]
  • Some 40%-70% of confirmed alcoholics report sleep disorders of various sorts. [Source]
  • One study, reported in the peer-reviewed scientific journal Sleep in 2010, concluded that six or less hours of sleep was associated with a 12% increased risk of death, but nine or more hours was linked with a 30% increase. [Source]
  • Studies on laboratory rats in the 1980s (and confirmed in more rigorous tests in 2002) have indicated that complete sleep deprivation leads to a gradual drop in body temperature, break-outs of sores and lesions (as the immune system breaks down), crazed and violent behavior, and ultimately death within as little as two to three weeks. [Source]
  • An individual’s ability to deal with sleep deprivation may well be genetic to some extent. It has been found that 10%-20% of the population have a mutation in a particular gene such that they experience a particularly strong homeostatic drive to sleep. Such a person may be much less likely to develop insomnia than the average person, but equally they may have much more difficulty coping with sleep deprivation, working a job that requires shift-work, etc. [Source]
  • The pioneering American sleep researcher William C. Dement himself went without sleep for 48 hours, and reported feelings of suspicion and paranoia, as well as vision problems and increased clumsiness. [Source]
  • A 17 year old Californian, Randy Gardner, went without sleep for 264 hours (11 days) for a bet in 1964, and currently holds the official scientifically-documented record for intentional sleeplessness without the use of stimulants, although British consciousness researcher Tony Right is also recorded as having achieved 11 days of sleeplessness in 2007, using a special raw food diet of his own devising. [Source]

Expert Bio

Dr. Brooke Dulka is a medical writer and neuroscientist. She recieved her Ph.D. in biological psychology from the University of Tennessee, and she is currently a postdoctoral researcher at the University of Wisconsin-Milwaukee where she studies the neurobiology of memory.


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