In hopes of getting a good night's sleep, one in five people now wear a sleep tracker, reports Pew Research.

Unfortunately, research into these devices has had mixed results: Some say they help you improve the duration and quality of your sleep, while others say they cause more harm than good.

Struggling to decide whether to use a sleep tracker? Learn more how the sleep trackers work, as well as the pros and cons of using one.

How Do Sleep Trackers Work?

Sleep trackers claim to measure your sleep quality and duration, but the reality is a bit more complex.

What most sleep trackers do measure is your movement and heart rate — and sometimes your breathing patterns or blood oxygen levels. Next, a proprietary algorithm, or set of rules, is used to make judgments about your sleep quality and duration.

For example, most sleep trackers have a sensor called an accelerometer. This measurement device detects movement. When you're still, the device assumes you're asleep. When your movement reaches a certain threshold, it assumes you're awake. This is how your sleep duration is calculated.

Pros of Using a Sleep Tracker

Market analysts predict the market for these devices will reach just over $7 billion by 2026, suggesting sleep trackers have undeniable allure. But what is it that makes them so attractive?

Here are four reasons to track your sleep:

1. You can manage what you measure. Dr. Kelly Baron, director of the University of Utah's behavioral sleep medicine program, claims this is the biggest benefit to monitoring your sleep. The idea is simple: If you can detect patterns in how your nighttime behaviors impact your sleep quality and duration, you can make changes to help you sleep better.
2. Sleep trackers may help with bedtime routines. Dr. Conor Heneghan, lead research scientist at Fitbit, argues that tracking your sleep makes you more conscious of when you go to bed and wake up each day. As a result, it may help you get the seven to nine hours of sleep you need.
3. Sleep trackers may help detect sleep disorders. Advanced sensors that measure your blood oxygen can flag the possibility that you have sleep apnea. However, a sleep study prescribed by your doctor will be required for an official diagnosis.
4. Sleep trackers may help you wake up. Some sleep trackers, which claim to differentiate between light and deep sleep stages, have special alarms that wake you up when you're closest to being awake. The theory is that you'll find it easier to wake up and be in a better mood as a result.

Cons of Using a Sleep Tracker

Some scholars say there's a gap between what marketers claim and what validity data proves. The thing is, technological advances happen faster than medical scholars can keep up with. But that's not the only problem with sleeping-tracking devices.

Here are five reasons not to track your sleep:

1. Sleep trackers introduce poor sleep hygiene. When it comes to proper sleep hygiene, viewing devices immediately before or after sleep is a no-no. A sleep tracker may incentivize people to break this rule, argues Dr. Baron and colleagues.
2. Sleep trackers may be inaccurate. Sleep trackers may suggest you get more sleep than you do in reality. This is especially true for trackers that rely on movement sensors, as you could simply be lying awake at night. They're also unable to accurately distinguish between light and deep sleep. “Even medically validated diagnostic technologies are at risk for false positive and false negative results," points out Massachusetts General Hospital's Kathryn Russo and colleagues.
3. Sleep trackers can worsen insomnia. Across three case studies, patients spent an excessive amount of time in bed trying to maximize their sleep duration. Unfortunately, that's known to exacerbate insomnia.
4. Sleep trackers make some people resistant to treatment. In the same study, patients trusted data from their wearable devices over results from official sleep studies. They also neglected evidence-based treatments for insomnia, instead preferring to go it alone.
5. Sleep trackers are tied to a sleep disorder. Some people who wear sleep trackers become preoccupied with optimizing their sleep data. This condition, known as orthosomnia, enhances your nighttime anxiety, which can make it harder for you to sleep.

Most Popular Sleep Trackers in 2020

Three sleep-tracking devices lead the market, each with its own features and benefits:

• Apple Watch Series 5. This smartwatch detects your heart rate, rhythm and electrical activity, plus your movement and respiration rate. However, it doesn't measure your blood oxygen levels. To use this device as a sleep tracker, it must be paired with a sleep-tracking app. Popular apps include AutoSleep, Sleep Watch, Pillow and Sleep++.
• Fitbit Charge 4. This smartwatch detects your movement and heart rate, but not your breathing patterns or blood oxygen levels. Based on this information, Fitbit presents an estimate of the time you spend in light, deep and REM sleep stages. It also gives you an overall Sleep Score, allowing you to track your sleep quality over time, and helps you wake up with Smart Wake.
• Garmin Fēnix® 6S. This smartwatch detects your movement, heart rate, breathing patterns and blood oxygen levels. Based on this information, Garmin reports your sleep duration (both restless and restful sleep) and estimates how long you spend in light, deep and REM sleep stages. It also shares your respiration rate, or how many breaths you take per minute, and the percentage of oxygen in your blood, which is helpful for detecting sleep apnea.

Sleep trackers are not medical devices. If you're struggling to get enough shut-eye, first seek medical advice from your primary physician.