When most people think about sleep, they treat it like a simple subtraction problem. “I went to bed at 10 p.m. and woke up at 6 a.m.,” the normal thinking goes, “Eight hours passed between my bedtime and wake time, so that means I got eight hours of sleep! I’m solid!”
Unfortunately, this isn’t how sleep actually works. And if you’re thinking about sleep in this way, it might be why you’re “sleeping” for the recommended seven to eight hours per night and still waking up exhausted each morning.
Why? Treating sleep like a subtraction problem focuses only on sleep quantity. It totally ignores sleep quality. If you spent eight hours in bed but you got up twice to use the bathroom, spent an hour tossing and turning, and spent zero time in restorative sleep stages, you didn’t really get eight hours of good sleep. It was probably more like four to five.
In contrast, if I spent six hours in bed but my sleep quality was excellent, I logged way more valuable sleep than you. I’ll have spent less time on sleep — and will appear to have underslept, relative to official recommendations which often look only at sleep quantity. Yet I’ll wake up feeling more refreshed and restored.
Sleep efficiency is the percentage of time you spend actually sleeping at night, versus lying awake in bed, getting up to have a snack or use the restroom, etc.
The higher your sleep efficiency, the less time you have to spend in bed each night in order to feel rested the next day. Sleep efficiency of 85% of higher is considered good.
Ready to enhance your sleep efficiency? Here’s how to stop obsessing about sleep quantity and start thinking about sleep quality.
Sleep when you’re sleepy
This might sound obvious. But as with the “obvious" advice “eat only when you’re hungry,” it’s something many of us struggle with.
Suppose that you’re concerned about getting too little sleep. You might try to get to bed earlier — before you actually feel tired — because you feel like you should be sleeping more, and you think having an earlier bedtime automatically means you’ll get more sleep.
Not so fast. Experts say that going to bed before you’re actually tired is a recipe for tossing and turning instead of sleeping, which kills your sleep efficiency and leads to fewer total sleep hours, not more. Instead of choosing an arbitrary bedtime, listen to your body’s cues. If you don’t yet feel tired, stay up and do something else until you get genuinely sleepy (and don’t feel guilty doing so).
Understand fatigue versus sleepiness
It’s also important to distinguish between fatigue and sleepiness. You might feel mentally and physically exhausted after a long day, but that doesn’t necessarily mean you’re sleepy. Trying to sleep when you’re fatigued instead of sleepy can also lead to tossing, turning, and insomnia. If you feel exhausted but also physically wired, you might be fatigued and not sleepy.
It sounds paradoxical, but sleep experts like Stanford’s Brandon Peters, MD, say “one of the most effective remedies for insomnia is to delay your onset of sleep.” Even if you feel fatigued, Peters insists “it’s critically important for people to only go to bed when they feel sleepy.” Do something low-key like bathe or sleep if you’re mentally or physically tired, and only go to sleep once you actually feel sleepy.
Fall asleep right
The average person takes about 10–20 minutes to fall asleep. If you’re in that range, then great — you’re on track.
If you take longer than 20 minutes to fall asleep, your bedtime routine might be to blame. According to Harvard University, good sleep hygiene is essential for getting to sleep relatively quickly. Establishing a set bedtime routine, staying out of your bedroom during the day (don’t work from home there, for example), and doing deep breathing or meditation to wind down before bed are all good ways to transition cleanly into sleep, improving your sleep efficiency.
Conversely, it’s actually possible to fall asleep too fast. If you fall asleep within five minutes of getting into bed, you might be overtired, or you could have a sleep disorder (see below). Ask yourself if you felt sleepy earlier than your bedtime last night, for instance. If you did, and you’re able to adjust your schedule, trying going to sleep earlier.
Just because you slept, that doesn’t necessarily mean that you slept well.
Broadly, there are three main stages of sleep.
- During light sleep, your body is either transitioning to sleep, or you’re asleep but you’re not yet sleeping deeply. Your heartbeat slows down and you’re getting rest, but your brain still experiences bursts of activity.
- During deep sleep, your muscles relax, your brain waves slow down dramatically, and your heartbeat slows well below your daytime resting heart rate. According to the National Institutes of Health (NIH), this is the kind of sleep “you need to feel refreshed in the morning.”
- Finally, during REM sleep your brain lights back up again with dramatic patterns of activity, but your body remains paralyzed. Why? In REM sleep, you’re dreaming, and your body doesn’t want you to physically act out your dreams. REM sleep is necessary for “memory consolidation” according to the NIH. In this stage, your brain is consolidating and building on what you learned or experienced during the day.
Spending the right amount of time in each sleep stage is critical if you want to have a good night’s sleep. You need a solid balance of light sleep, deep sleep (to feel physically refreshed), and REM sleep (to feel mentally refreshed) each night. If you spend too little time in a given stage, you might wake up feeling physically or mentally tired, despite sleeping for the “right” number of total hours.
Here’s how to achieve the right balance.
According to Johns Hopkins, getting exercise during the day is a great way to increase the time you spend in the deep sleep stage. Though they don’t know the exact reasons why, scientists have found that getting 30 minutes of moderate aerobic exercise during the day is enough to increase deep sleep. The effect is fast — if you exercise during the day, you’re likely to get more deep sleep that same night.
One caveat: Don’t exercise too late in the day, or the exercise itself might interfere with getting to bed. Johns Hopkins recommends allowing one to two hours between exercise and your bedtime so your body can wind down fully.
Time substances right
If you have a couple of drinks before bedtime, you’ll probably fall asleep fast. But you’ll wake up in the morning feeling groggy and terrible.
Why? Although alcohol might make it easier to get to bed initially, Harvard University says that it also disrupts REM sleep, robbing you of the critical time you need in that sleep phase in order to feel mentally restored. Once the booze wears off in the middle of the night, you’re actually more likely to wake up frequently, too.
The end result is that a nightcap — while it may appear to fight insomnia by getting you to bed faster— actually leads to lower quality sleep, leaving you feeling more tired (especially mentally, due to the lack of REM sleep) the next day.
Likewise, Harvard says that drinking too much caffeine can disrupt deep sleep, or cause you to get up in the middle of the night to pee, messing with sleep efficiency.
If you’re going to use these substances, get the timing right in order to minimize the risk to your sleep quality. Harvard says you should avoid caffeine after 2 p.m. (after 12 p.m. if you’re especially sensitive). With alcohol, stop drinking at least a few hours before bedtime.
Light at the right times
Light plays a huge role in mediating sleep. Humans have a built-in circadian clock, but it’s not that accurate. To keep it in tune with the days, our brains rely on exposure to bright sunlight in order to reset our circadian clocks, aligning them to the day’s 24-hour cycle.
That’s both a curse and a blessing. In today’s environment, many of us bathe our eyes in bright light from home lighting, and TV and phone screens at night. This tricks our brains into thinking the evening is actually the daytime, which messes up our circadian rhythms and disrupts our sleep. Blue light is especially problematic.
To protect your circadian rhythms, turn your house’s lights down at night, avoid screens right before bedtime, and enable blue light filters on any devices you use before bed. This will help to prevent bright, blue lights from tricking your brain into thinking it’s morning when it’s actually night. Make sure your room is as dark as possible during sleep, too.
Conversely, it’s important to get enough light exposure during the day. Bright light in the daytime sends your brain the signal “Stay awake!” leading to better wakefulness during the day, and better sleep at night. A study in the Journal of Clinical Sleep Medicine showed that people who got light exposure in the day slept an average of 46 minutes longer at night and had better sleep quality than those who didn’t.
Fix medical sleep problems
These are all strategies to optimize your sleep quality if you’re an overall healthy sleeper. According to the Cleveland Clinic, though, as many as 70 million Americans have sleep disorders — medical problems which mess with sleep quality.
One of the most pernicious is sleep apnea, a condition that affects your breathing during sleep. Many people don’t even know they have the condition, yet it can rob you of quality sleep as well as increase your risk of conditions like heart disease.
Likewise, sleep stage imbalances can signal deeper problems. People suffering from depression often get too much REM sleep, for example, which means they spend less time in other sleep stages, disrupting their overall sleep balance. Medications, too, can impact sleep in unpredictable ways.
That’s why if you’re concerned about your sleep, it’s a good idea to check in with your doctor. Treat medical sleep problems first; once those are resolved, you can pivot to optimizing sleep quality.
How do you know whether you’re getting quality sleep? A wearable device can help. I like the Fitbit Sense smartwatch. It automatically tracks your sleep, telling you what time you fell asleep each night, how much you woke up in the night, and how much time you spent in each sleep stage. The Amazon Halo band is cheaper and has similar functions.
Here’s the best news. No one night is going to make or break your sleep — even if you have a terrible night and only sleep four hours, it’s okay, and you don’t need to stay up stressing about it. All of the strategies I’ve shared here are about making long-term lifestyle tweaks that can optimize your sleep quality over weeks or months. By applying these strategies, you can increase your average sleep quality, leading to better sleep over the long run, even if one night isn’t perfect.
They can also potentially allow you to sleep for fewer hours and still feel just as rested in the morning, freeing up time for other things — especially if you’re forcing yourself to go to bed earlier than your body wants to, or you’re wrecking your sleep with too much alcohol or caffeine.
Stop focusing on sleep quantity, and start optimizing sleep quality. Your body will thank you.
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