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Sleep Efficiency: Why It Is Necessary but Not Sufficient

Sleep efficiency can be a helpful way to understand how well you’re sleeping, but the best “score” for understanding your sleep health is sleep debt.
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What is the best way to improve sleep efficiency? If you’ve ever found yourself lying wide awake in bed, you may have indeed wondered how you can spend more of your hours in bed actually asleep. While we’ll definitely clue you into how to improve sleep efficiency, it’s worth noting it is not the only relevant metric that tells you how well you sleep. It is also essential to consider your sleep debt, which factors in your individual sleep need. Before we examine each metric in detail, let’s first consider how sleep efficiency is defined.

Read on to learn more about the sleep efficiency and sleep debt metrics, what causes poor sleep efficiency, how sleep efficiency relates to sleep debt, how to improve your sleep hygiene for better sleep, and how the RISE app can help.

What Is Sleep Efficiency?

Sleep efficiency is the ratio of your total sleep time to the total amount of time you spend in bed, typically multiplied by 100 to convert it to a percent. For example, if one night you spent eight hours in bed but were only asleep for six of those hours, your sleep efficiency for that night would be 75% (6 / 8 = 0.75 x 100 = 75%). Sleep efficiency above 85% is considered good; below this is typically considered insomnia. Keeping it above 90% is ideal. That said, good sleep efficiency does not guarantee you are getting a sufficient amount of sleep.

This is because sleep efficiency doesn’t take into account your sleep need. Your sleep need is the number of hours of sleep your body needs each night, and it is genetically determined (similar to height or eye color). There is variability in your individual sleep need over your own lifespan, but on average, a person needs 8 hours and 10 minutes of sleep each night (give or take 44 minutes), and about 13.5% of the population needs 9 hours or more. If your individual sleep need is 8.5 hours, and you only spend 7.5 hours in bed each night, you will accrue sleep debt no matter how high your sleep efficiency is.

Sleep debt is defined as the total number of hours of sleep you missed relative to your individual sleep need over the past 14 days. Sleep debt over roughly 5 hours will interfere significantly with your well-being. While sleep debt is a more important metric than sleep efficiency, the strategies for tackling sleep efficiency will also help lower your sleep debt. Both can be improved through good sleep hygiene, a set of daily behaviors that impact your sleep (more on this later).

Keep in mind, neither of these metrics are synonymous with your “quality of sleep.” If you improve your sleep efficiency, you may improve your subjective sleep quality as well as objective assessments of your sleep (e.g., polysomnography). However, there is no consensus among sleep scientists as to what “sleep quality” actually means. Instead, it’s more important to focus on sleep duration and work to improve any habits that could be interfering with you getting the sleep you need.

What Causes Poor Sleep Efficiency?

Sleep efficiency: Man who can't sleep lying awake in bed

If you have poor sleep efficiency — your sleep duration is much lower than the total amount of time you spend in bed — there are two issues to consider: sleep latency and sleep fragmentation.

  • Sleep latency: Also known as sleep onset, this is the amount of time it takes you to fall asleep after getting into bed. Ideally, it should take no more than 30 minutes.
  • Sleep fragmentation: This refers to intermittent waking throughout the night. Waking up a couple of times is normal, especially at the end of a sleep cycle. (A sleep cycle comprises a few different sleep stages in succession, including light sleep, deep sleep, and REM sleep, and a full sleep cycle typically lasts between 90 and 110 minutes.) In addition to natural stirrings in the night, sleep fragmentation can be caused by sleep disruptions out of our control, such as a toddler or a pet waking us up.)

Both factors contribute to sleep efficiency by adding time you are lying awake in bed. If you regularly take longer than 30 minutes to fall asleep, and/or if you repeatedly wake up most nights, your average sleep efficiency is likely to be low. There are a variety of potential reasons why this may be the case, but the most likely culprit is poor sleep hygiene

As mentioned above, sleep hygiene refers to behaviors that affect your sleep. This includes all your daily behaviors, not just what you do right before getting into bed — a common misconception. We’ll discuss some ways to improve sleep hygiene later on, which in turn will help you improve your sleep efficiency.

If you regularly have issues with sleep latency and sleep fragmentation despite following all the best practices for good sleep hygiene, it could be a sign of a sleep disorder. Many sleep disorders are associated with poor sleep efficiency, such as obstructive sleep apnea. Consider talking to your healthcare provider about trying polysomnography (a sleep study) to determine your actual sleep efficiency and potentially diagnose any underlying problems. Your doctor may prescribe sleep medicine or other sleep aids.

Learn more about why it takes you so long to fall asleep here.

How Sleep Efficiency Relates to Sleep Debt

Poor sleep efficiency can cause feelings of daytime sleepiness. More importantly, it can contribute to sleep debt. Missing out on sleep while lying in bed can contribute to sleep debt just like staying up too late or waking up too early. That said, even if your sleep efficiency is good, you can still accrue sleep debt.

One reason this is the case is that many people make the mistake of conflating the time they spend in bed with the time they spend asleep. But in order to avoid sleep deprivation, you need to take your sleep efficiency into account and plan a sleep schedule that allows you to stay in bed longer than the total number of hours of sleep you need.

For example, let’s say you need nine hours of sleep, so you stay in bed for nine hours. However, it takes you 20 minutes to fall asleep, and you wake up four times during the night, each time staying awake for about 10 minutes. Your sleep efficiency in this case is approximately 89%, which is pretty good, but you’ve acquired an hour of sleep debt. 

The effects quickly accumulate if you do this every night. In fact, missing one hour of sleep for 10 consecutive nights can lead to the same consequences as staying up for 24 hours straight, which is functionally equivalent to having a blood alcohol level of 0.10% (higher than the legal limit for driving in all 50 states). 

That said, you can recover from one night of poor sleep relatively quickly, as long as you prioritize surpassing your sleep need by sleeping longer at night (or taking well-timed naps) until you are caught up. Your sleep debt includes missed sleep from the past 14 days, so keeping it low most of the time (under five hours) will give you some wiggle room for those occasional late nights or early mornings.

Another reason you can accrue sleep debt even while maintaining high sleep efficiency is that you may be underestimating your sleep need. If you underestimate your sleep need, you will accrue sleep debt no matter how high your sleep efficiency is. It is therefore crucial to learn your personal sleep need and make sure you plan enough time in bed (longer than your sleep need) to be able to meet it. The RISE app will tell you your sleep need based on your sleep data.

How to Improve Your Sleep Efficiency With Good Sleep Hygiene

As mentioned above, the most effective ways to raise sleep efficiency (in the absence of a sleep disorder) are all about sleep hygiene. There are many benefits to improving your sleep hygiene. Not only will it help you raise your sleep efficiency, but as we’ve mentioned, and most importantly, it can also help you pay back sleep debt. In short, improving your sleep hygiene will help all aspects of your sleep, which in turn will improve your mood and energy levels throughout the day.

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Be Smart About Light Exposure

Light is a strong cue for your circadian rhythm, so you need to be mindful of the right times to expose yourself to it.

Getting sunlight first thing in the morning is a great way to signal to your body that it’s time to wake up. Sunlight exposure suppresses the sleep-promoting hormone melatonin and triggers the production of the crucial neurotransmitter serotonin (which regulates mood and converts to melatonin about 12 hours later when it’s time to sleep). It’s good to get outside in the morning even when it’s cloudy, but you can substitute sunlight for artificial bright light when necessary.

Conversely, you should avoid light at night, especially blue light, as it interferes with your body’s production of melatonin. Wear blue-light blocking glasses when using electronic devices in the evening.

Get Exercise During the Day

Exercise increases adenosine, a compound that builds up in your brain during your waking hours to create sleep pressure, allowing natural sleep to come more quickly. That said, avoid exercising in the evening, as it can interfere with your body’s production of melatonin. The best time to exercise is in the morning or early afternoon.

Avoid Caffeine and Alcohol in the Evening

RISE app screenshot telling you when to limit caffeine
The RISE app will remind you when it's time to stop consuming caffeine for the day.

Caffeine is a well-known stimulant, and consuming it too close to bedtime can interfere with your sleep. By contrast, alcohol is a sedative, so you may think it will help you sleep. On the contrary, while alcohol may make you feel sleepy initially, it can actually increase sleep fragmentation throughout the night. It is best to avoid it if you’re trying to improve sleep efficiency. The RISE app will tell you the exact cutoff times for both caffeine and alcohol.

Have a Wind-Down Routine

This is similar to a bedtime routine, but the idea is to extend this routine beyond bedtime. It can begin as early as a couple of hours prior to your bedtime. Listen to some relaxing music, do some light reading, write in your journal, take a warm bath or shower, and/or do anything else you know will help you relax. By that same turn, avoid anything that will stimulate you mentally or physically and stave off sleep. The idea is to relax your mind and body and prepare yourself for sleep. The RISE app will remind you when it’s time to wind down and allow you to plan your routine.

Prep Your Sleep Environment

Make your bedroom a sleep sanctuary, focusing on these three main elements:

  • Keep it cool: Body temperature starts to drop in the evening, a necessary precursor to sleep, eventually falling as much as 3 degrees Fahrenheit. This most likely happens in order to conserve energy during sleep. For this reason, a cooler external temperature can further encourage sleep. Use a fan, an open window, or an air conditioning unit to help cool down your room if it’s too warm.
  • Keep it dark: As mentioned above, you will want to avoid bright light and blue light at night. It’s best to keep your bedroom free of light as much as you can while you sleep. Turn off any devices that don’t need to be on, and use an eye mask (unless it’s so dark you can’t see your own hands).
  • Keep it quiet: As much as possible, keep your bedroom free of noise while you sleep. For noise outside of your control, use earplugs to help block it.

Go to Sleep During Your Melatonin Window

Your Melatonin Window is an hour-long period in the evening during which your body produces peak levels of melatonin to prepare you for sleep. When it begins each evening will depend on the previous day’s schedule, but if you keep your schedule consistent, it will happen around the same time every day. It is best to go to bed during this window, as this can help to reduce sleep latency and sleep fragmentation. The RISE app will tell you exactly when this window begins each day.

When All Else Fails, Try a Sleep Reset

If you’ve been lying in bed for more than 30 minutes and still feel wide awake, it may be best to get out of bed. This might seem counterintuitive, especially if you’re dealing with sleep debt, but continuing to toss and turn in your bed while feeling increasingly frustrated is not going to do you any favors. (Not only will it decrease your sleep efficiency, but it also might lead to associating your bed with sleeplessness, a common element of insomnia.)

Once out of bed, your goal is to do something that will help you feel sleepy. Sit somewhere comfortable, and try any of the more effective activities in your wind-down routine. The RISE app also has guided relaxation exercises for those times when you just can’t seem to get yourself to relax. 

Above all else, try not to beat yourself up when this happens. Take a few deep breaths, and remind yourself it is perfectly normal to feel overstimulated sometimes. Your mental health and overall wellbeing will thank you.

Use the RISE App to Improve Your Sleep Habits

RISE app screenshot showing how much sleep debt you have
The RISE app calculates your current sleep debt, the most important metric when it comes to improving sleep.

Good sleep efficiency is definitely something worth striving for, and as a metric, it can give you a sense of how well you’re sleeping and whether you need to improve your sleep hygiene. However, it doesn’t give you a complete picture of your sleep health and is not the end-all, be-all metric.

Essential is knowing your individual sleep need, which will clue you into your current sleep debt, the most important metric there is for sleep and next-day energy. The RISE app will tell you your sleep need and calculate your sleep debt at any given time, allowing you to use this information to get the right amount of sleep so you can feel and function at your best.

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RISE makes it easy to improve your sleep and daily energy to reach your potential

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