How to Measure Sleep Performance

Making sense of all that data from your sleep tracking apps.

By Andrea Pisani Babich

There’s tons of talk about improving your sleep hygiene, but how do you track if your sleep is actually getting better? 

The obvious way is to consider how you feel. Are you falling asleep more quickly? Are you staying asleep throughout the night? And are you waking up feeling well-rested? Then your sleep has probably improved. 

But if you want more tangible data to record your progress, a sleep tracking device can help by recording your sleep patterns. While they’re not as comprehensive as a clinical sleep study, many of the sleep apps available on iOS and Android give you plenty of information to assess the quality of your sleep on any given night (or day) and recognize patterns through stored historical information on your sleep performance.

The next hurdle to overcome is learning how to interpret if what you’re seeing is good or not so good. We’ll tell you everything you need to know about tracking your sleep performance so you can keep up with your sleep health. 

Woman sleeping

What Does Quality Sleep Look Like? 

Up until the 1950s, scientists believed that our brains powered down during sleep and simply recovered from the toils of the day. While they were right about the recovery part, they discovered that our brains are far from turned off while we sleep. In fact, some pretty complicated processes occur that we still don’t fully understand.

Sleep occurs in four stages that are divided into non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. We spend the majority of our sleep time in the NREM phase during which time our brains generally slow down and transition to REM sleep. NREM sleep is further broken down into three distinct stages that in combination with REM sleep comprise one sleep cycle.

Understanding the Sleep Cycle

Stage 1

N1: This transitional stage of light sleep lasts up to seven minutes and shifts our brain functions from wakefulness to sleep. Our eyes are closed, but we can still be easily awakened. Brain waves and muscle activity begin to slow down, including heartbeat, breathing and eye movements.

Stage 2

N2: This light sleep stage lasts about 10 – 25 minutes. We spend about half the night in N2 sleep, during which time our heart rate continues to slow, our body temperature drops, and eye movements stop altogether. Brain waves become even slower with occasional bursts of rapid activity called sleep spindles.

Stage 3

N3 or Deep Sleep Stage: We are harder to wake up during this deep sleep stage that generally lasts 20 – 40 minutes. Sleep experts define this stage by the presence of more than 20% slow wave activity (SWA) in the brain. Later in N3, your brain will engage in more than 50% SWA. 

Even without an EEG, your sleep app will recognize SWA by recording much slower breathing and heartbeat. In fact, your heartbeat and breathing are slower during N3 than at any other time during the night.

What’s happening during all this time of slow brain activity? Turns out, a lot. We need about five undisturbed N3 stages of sleep each night in order to feel refreshed in the morning. Many scientists believe that during this deep sleep stage, we experience restorative sleep—our bodies repair and regrow tissues, build bone and muscle, and strengthen our immune systems.

Stage 4

These three NREM sleep stages are followed by REM sleep. The first REM stage should occur about 90 minutes after you fall asleep and may last about ten minutes. Subsequent REM stages get longer with the final one lasting up to an hour.

Related: What is REM rebound?

Unlike NREM stages when your body is slowing down many functions, your brain actually becomes more active during REM sleep. Your heart rate increases and your breathing becomes more rapid, irregular and shallow. 

And, as the name suggests, you experience rapid eye movements, possibly related to the dreams you have during this stage. REM sleep comprises about 20 – 25% of total sleep in a typical healthy adult.

Tracking Sleep Performance

Healthy adults cycle through these four stages of sleep five or six times each night every 90 minutes or so. So what should a typical night look like in order for you to feel rested and restored? 

Related: Best sleep calculators

In addition to the recommended seven to eight hours of sleep we need each night, the following are some sleep performance goals for a good night’s sleep. A sleep health app or a sleep tracker with all the bells and whistles will measure and record the following metrics:

Heart Rate

Your heart rate should show a pattern of gradually decreasing to a level at least 10% lower than your average waking heart rate. After that, it should increase while you experience REM sleep every 90 minutes or so.

Breathing Patterns

Your breathing patterns should follow the pattern of your heart rate, decreasing in rate as you fall asleep and increasing after bottoming out during deep sleep (N3). 

Duration Spent in Each Stage of Sleep

While every sleeper is going to be different, here is the average amount of time you should be spending in each sleep cycle.

  • N1: 1 to 7 minutes
  • N2: 10 to 25 minutes
  • N3: First episode lasts 45 to 90 minutes with episodes getting shorter as the night progresses
  • REM: 10 minutes then getting progressively longer up to one hour

Number of Times Awakened

This number changes as we age, and what is tolerable for some people may feel like torment for others. Studies show that young adults wake up about five times a night, but some people over 60 can wake as many as 150 times per night, although they may not remember most of the episodes.

Sleep experts suggest that if you wake more than four or five times a night and feel tired in the morning, you should consult a sleep specialist to determine the cause of your waking and to find a solution.

How to Improve Sleep Performance

After you’ve started tracking your sleep health on a fitness tracker, Apple watch, or other sleep tracking device, you can do a sleep analysis to see where you’re having issues. It can also be helpful to keep a sleep diary for tracking your sleep habits.

If your sleep is not improving over time, it may be time to speak with a sleep specialist. All of the data you’ve recorded on your sleeping patterns can come in use when speaking with a physician. For instance, if you’ve been experiencing abnormal breathing patterns (something you may not know had you not tracked it with a device) your doctor will have a good starting point for treatment. 

You can also try sleep remedies to improve your sleep. What you need may be as simple as a wind down routine or less caffeine in the evening.   


You wouldn’t think that something as basic as sleeping would require so much effort, but for many people sleep is as elusive as it is vital to our health. Gathering information on your sleep performance with a sleep app may help to explain why you feel tired all the time. Once you see how well you are sleeping (or not), you can begin to take steps to improve your sleep, in terms of both quality and quantity. Happy cycling!

Still have questions about your sleep performance data? Drop us a line; we’ll be happy to answer your questions.

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