What is sleep debt?
What is sleep debt?
Sleep debt, or sleep deficit, is the accumulated loss or difference between the hours of sleep your body needs and how many hours you actually get. For example, if you find you need 8 hours of sleep on average, but only get 6 hours of sleep due to problems falling or staying asleep, your sleep debt would be 2 hours. Sleep debt is cumulative as well, so if you’re struggling with jet lag in a new time zone and losing 2 hours of sleep every night for a week, your sleep debt would actually be around 14 hours.
Sleep debt can add up quickly based on any type of sleep interruption or change in your sleep schedule. If you decide to start waking up just half an hour earlier than you’re used to, you could easily rack up 3.5 hours of sleep debt by the end of just one week. While setting your alarm 30 minutes early might not feel like a huge shift, the effects of this can compound and take their toll if you don’t make any other changes to your sleep schedule. As sleep debt builds, there are many ways our brain and body functions can deteriorate.
Inadequate sleep over time causes sleep debt to build and can subtly or directly affect your wellbeing.
What happens when you have sleep debt?
Sleep debt can lead to many negative consequences on your health and sleep. While you’re probably already familiar with why we need good sleep, it should come as no surprise that sleep deprivation and exhaustion can lead to:
- Tiredness throughout the day
- Difficulties with focus, concentration, and productivity
- Weakened immune function
- Increased blood pressure
- Lower emotional intelligence and feelings of social detachment
- Reduced capacity to form and access memories
- Greater risks for obesity, diabetes, hypertension, cardiovascular and coronary heart diseases, and other health issues
Research has shown that we can even adapt to chronic sleep restriction or high sleep debt so we don’t feel as tired, even though our brains and bodies might be operating at reduced mental and physical capacities.
How do you know how much sleep you need?
The average person needs 7.5 hours of sleep a night. The ideal amount of sleep varies person to person because of a couple different factors, including your sleep drive, and the length of your sleep cycle. Your sleep drive is determined by genetics, so if you know your parents are the type of people who need more or less sleep than average, odds are you are the same way.
Your sleep drive influences how long and how many sleep cycles your body needs a night. If you know about sleep cycles, you might have heard about 90 minute sleep cycles and assumed they were one size fits all, when in reality, they vary from person to person. On average, we need 5 full cycles of 90 minutes each, which works out to 7.5 hours of sleep a night.
To figure out how many hours of sleep you need, try sleep specialist Dr Michael Breus’s trick: count back 7.5 hours from your normal wake up time and use that as your bedtime for a week.
The goal is to sleep enough that your body will wake up naturally. After trying your new set bedtime for 7 to 10 days, you should start waking up 5 minutes before your alarm. If you're not waking up more refreshed or easily, try moving your bedtime back again, another half hour earlier, and continue to do so until you can wake up without your alarm.
Trying a new bedtime can be a hard switch to get used to, but setting a standard time for sleep will help regulate your circadian rhythm, and also likely help you catch up on your sleep debt!
How can you make up for lost sleep and recover from sleep debt?
Napping can be a good way to make up for lost sleep, but it can also hurt your overall sleep schedule. Some people wake up more sluggish and foggy after a nap because their bodies were expecting to get more sleep. For many, it can also make it harder to fall asleep later in the evening. Short naps (between 10 and 20 minutes) are generally better for boosting your energy and not interfering too much with your regular schedule. Naps taken too close to your bedtime can also disrupt your nightly rest; a good rule of thumb is to only nap in the first half of your day, or closer to your wake up time than your bedtime.
Sleeping in is another way to help make up for extra sleep debt. Just like with napping, it can be harmful to your sleep schedule if you do it too much, but sleeping in on the weekends actually does reduce sleep debt, and can make you feel more refreshed for, and during the week!
Ultimately, the best way to reduce or eliminate your sleep debt is to figure out the right amount of sleep for you, set the right bedtime for your needs, and try to get the right amount of rest to match your sleep drive. Improving your sleep hygiene and working on repaying your sleep debt will help you regulate your circadian rhythms so you can get the sleep you need and wake up actually refreshed.