By Jack Harley, MSc, University of Oxford 

We all know how important sleep is for our overall health, and the detrimental effects of losing sleep. In fact, losing sleep on a regular basis can lead to accumulating sleep debt. This is the difference between how much sleep you need and how much you actually get. 

Sleep debt adds up over time, and can negatively impact your health. However, by improving your sleep habits, you can reduce your sleep debt and improve your health.

What is sleep debt?

Sleep debt is the difference between how much sleep you need, and how much sleep you actually get. Sleep debt builds from one day to the next, and is cumulative. 

For example, if you get 4 hours of sleep per night when your body needs 7, you will have a sleep debt of 3 hours. If you follow this pattern each night for a week, you will have accumulated 21 hours of sleep debt. 

Even if you only lose 20 minutes of sleep per night, it can quickly add up over time. Therefore, it is important to go to ensure you get enough rest each night, to ensure you are not losing sleep. 

Do you feel tired if you have sleep debt?

Just because you have sleep debt, doesn’t necessarily mean you feel tired. Studies have shown that your brain adapts to chronic sleep deprivation, to prevent you from feeling sleepy. This means that you may have sleep debt without feeling physically or mentally tired, but still have the physical and mental effects of sleep debt. 

Consequences of sleep debt

Sleep is vital for health, and sleep debt can result in a range of consequences that may impair your ability to function during daily activities. Some of the long-term impacts of sleep debt are listed below: 

Mental fatigue and cognitive impairment

Sleep is crucial for allowing us to feel rested and able to concentrate during the day, and is also important for our cognitive functioning. Significant sleep debt may lead cognitive problems such as:

• Fatigue and drowsiness during the day
• Loss of productivity at work or school
• Cognitive decline including impaired memory 

Chronic disease

During sleep, the body undergoes repair processes which keep you healthy. Ongoing sleep deprivation associated with sleep debt may also increase the risk of a range of chronic health conditions, such as:

• High blood pressure
• Type 2 diabetes
• Obesity
• Cardiovascular disease 

Psychological problems

In addition to the physical health conditions, chronic sleep deprivation has also been shown to increase the risk of psychiatric illnesses such as anxiety and depression.

Luckily, getting enough sleep to repay your sleep debt, and avoiding more sleep debt can help reverse the risk of these diseases. 

 

Avoiding sleep debt

To ensure optimal health and wellbeing, It is best to try and establish healthy sleep habits to avoid sleep debt. Avoiding sleep debt requires knowing how much sleep your body needs per night, and improving your sleep habits to get this amount regularly. 

Several tips can help to reduce sleep debt, such as: 

1. Find out how much sleep you need
   To determine how much sleep you need, note how you feel after different lengths of sleep.
   The amount of sleep you need per night varies from person to person, though adults generally require at least 7 hours of sleep per night, while teenagers require 8 or more hours. Children are recommended to get between 9 and 11 hours of sleep per night.
2. Record how much sleep you get
   Record how much sleep you get per night, so you can ensure you are getting the amount you need. This can be done by noting the number of hours you slept. Apps such as OnTimeHealth allow you to track your sleep conveniently on a regular basis.
   It is important to note that sleep is not a uniform process. Many of the most important stages of sleep occur later in the night, such as REM sleep, meaning it is not only important to get enough sleep, but to ensure you are getting high quality sleep. Too little time spent in REM sleep or deep sleep can leave you tired the next day, even if you get a full 8 hours of sleep.
   Alternatively, you can use a wearable sleep tracking device such as an Apple Watch or an Oura ring to automatically record how much sleep you are getting. These devices often allow you to track the amount of time you spend in each stage of sleep, so you can ensure you are getting quality rest.
3. Build a bedtime routine
   To ensure you can quickly fall asleep after getting into bed, try and build a maintain a bedtime routine. This is a series of actions that you take on a regular basis at night to prepare your body for sleep. A bedtime routine could include turning off electronic devices, dimming the lights in your home, and taking a shower. Research has shown that a bedtime routine can improve sleep quality.
4. Optimize your circadian rhythm
   Circadian rhythm refers to the bodily and psychological changes that occur over a 24-hour period. Circadian rhythm controls the sleep-wake cycle, and is affected by signals such as light and food intake.
   Try to align your body’s natural clock with the rising and setting of the sun to ensure you sleep well each night. The following tips can help to improve circadian rhythm:
   – Try to get sunlight exposure early in the day. Generally, at least 30 minutes of daylight as soon as you can after waking up is recommended
   – Avoid consuming caffeine after 2 p.m. in the afternoon
   – Exercise during the day to help you sleep better at night, but avoid exercising within 2 hours of when you plan to sleep as this can make it harder to sleep
   – Try to eat all of your food for the day within the same 8 to 12-hour period each day. This is known as intermittent fasting.
5. Go to bed at the right time
   Figure out what time you will need to go to sleep each night to get your required amount of sleep. Then, go to sleep 15 minutes earlier each night until you are regularly sleeping at your desired bedtime. Try to go to sleep and wake up at the same time each day, and avoid the temptation to sleep in on the weekends, as this can interfere with your circadian rhythm.
6. Set up your bedroom for sleep
   Make necessary changes to your bedroom so that it is properly set up for a good nights’ sleep. This includes:
   – Removing any electronic devices that emit lights during the night. Even low levels of light have been shown to interfere with sleep quality.
   – Ensure the room is as dark as possible, by using blackout blinds
   – Make sure your room is the appropriate temperature for sleep.
   – Ensure you have comfortable, soft bedding, including pillows, sheets and a mattress

Benefits of getting more sleep

There are several benefits of catching up on lost sleep. While it may seem like a waste of time, sleep is a crucial activity that allows your mind and body to perform at their best. Therefore, repaying your sleep debt can help you become healthier, fitter and more productive at work and is almost always worth doing. 

Cognitive performance 

Improving your sleep can improve cognitive performance. Research has shown that getting a full night’s sleep is associated with benefits to memory and attention. This in turn can allow you to be more focused and productive at work or school. 

Health and longevity 

In addition, regularly getting a good night’s sleep can help your body to stay healthy. It helps your blood pressure low, appetite properly regulated, and hormone levels in check. Adequate sleep also helps to boost your immune system and repair cells and tissues in the body. 

Over the long-term, getting quality sleep may also improve your longevity, that is, how long you live. 

Dealing with sleep debt

Losing sleep is often unavoidable if you lead a busy life. However, the only way to get rid of sleep debt is to sleep more. If you have accumulated a lot of sleep debt, paying it back may be a long-term process, and you may need to rely on napping in the short-term. 

Napping 

In the short-term, you may need to improve your ability to function by taking naps, if you have built up a lot of sleep debt. Consider taking 15-20 minute naps during the day to help you pay off your sleep debt. Naps can help you feel more refreshed and able to handle activities during the day. 

Research has shown numerous benefits associated with naps in people with sleep debt, such as:

• Reduced fatigue
• Improved energy levels
• Improved cognitive performance

When napping you should avoid napping for longer than 20 minutes, as you may enter deeper stages of sleep which may leave you feeling groggy and impact your nighttime sleep. 

Repaying Sleep Debt

It is important to try and repay your sleep debt, as much as realistically possible, by sleeping more. You should try to make up for your sleep debt by improving sleep hygiene and changing your relationship with sleep if necessary. 

1. Change your relationship to sleep
   In order to stop accumulating sleep debt, you may need to change how you think about sleep. Rather than thinking of sleep as a chore, try to think of it as an investment in your health. Remember, sleep is critically important for physical and mental health, and can impact many areas of life. Making the conscious decision to prioritize sleep is often the first step to improving the quality of your nightly rest. 
2. Improve your sleep hygiene
   In order to repay your sleep debt, you should aim to get more sleep each night. One way to do this is by improving your sleep hygiene, which refers to the habits and behaviors that help you get a good night’s sleep. 

There are several practices you can take up to improve your sleep hygiene, such as:

• Building a bedtime routine 
• Keeping light and noise levels low in your bedroom
• Minimizing the use of electronic devices at least 2 hours before you plan to sleep
• Going to sleep and waking up at the same time each day, even on weekends
• Keeping your bedroom only for sleep and sex 

Conclusion

It is often tempting to sleep less in order to be more productive during the day. However, regularly depriving yourself of sleep can lead to the accumulation of sleep debt. 

Sleep debt refers to the deficit between the amount of sleep you need and the amount of sleep you actually get. The more sleep debt you accumulate, the greater your risk of negative health complications. 

Fortunately, sleep debt can be repaid by sleeping additional hours. By making changes to your daytime and nighttime routines, you can improve your circadian rhythm and begin repaying your sleep debt.

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