Tracking Sleep: The Technology Behind Your Watch

Sleep tracking watches are equipped with features such as heart rate monitors, SpO2 trackers, and activity trackers to monitor sleep patterns. They can track sleep duration, sleep quality, and sleep phases. Sleep tracking watches can also record the sleep environment and lifestyle factors that may impact sleep. While these watches can provide valuable insights into sleep patterns, they do not directly measure sleep. Instead, they estimate sleep by measuring inactivity and slow heart rate. It is important to note that the light and radiation from smartwatches may cause a disturbed sleep cycle for some users.

Heart rate and pulse

Smartwatches use heart rate sensors to monitor your heart rate and track your sleep cycle closely. Some watches also track your breathing rate, which can give you greater insight into your overall health. Your respiration rate is considered the most important parameter of physiological data because it clearly indicates sleep disorders such as snoring and sleep apnea.

While a smartwatch can track your sleep, it does not measure sleep directly. Instead, it measures your inactivity and makes a guesstimate about how much you're sleeping. For exact data about your sleep habits, you would have to do a medical sleep study that monitors brain waves to analyze the stages of sleep.

If you want to understand your sleep pattern and track your sleep, it is recommended that you wear your smartwatch to bed. However, some people find it uncomfortable to wear a watch while sleeping. The light or strap on the watch can sometimes lead to a disturbed sleep cycle. Additionally, some people are concerned about the radiation emitted by smartwatches.

Sleep duration

Sleep tracking watches can help you understand your sleep patterns and track your sleep duration. They can record when you fall asleep and when you wake up in the morning by tracking your inactivity. Some watches, like the Apple Watch, can also track your sleep without needing to be told that you're about to sleep. You can also set up a sleep schedule, including a sleep goal (how many hours of sleep you want to get) and a bedtime reminder.

Sleep tracking watches use a variety of methods to track sleep duration. Many watches use accelerometers, which are small motion detectors that measure how much movement you're making while you sleep. This data is then analysed using an algorithm to estimate sleep time and quality. Some watches also use heart rate and pulse to track sleep. As your heart rate and pulse slow down, the watch can detect that you're reaching a deeper level of sleep. Watches can also track your breathing rate as you sleep, which can give you insight into your overall health. Additionally, some watches use a microphone to capture noise from the room or your body, and can measure your respiration to detect snoring, sleep apnea, and how often you wake up during the night.

While sleep tracking watches can provide valuable insights into your sleep duration, it's important to note that they don't directly measure sleep. Instead, they estimate sleep by measuring inactivity and other indicators. For exact data about your sleep habits, a medical sleep study that monitors brain waves would be necessary. Additionally, some people have expressed concerns about the radiation emitted by smartwatches and its potential impact on health. If you're considering using a sleep tracking watch, it's recommended to take it off for a few hours to let your skin breathe and prevent bacteria buildup.

Sleep quality

Some watches can also track sleep phases, including light sleep, deep sleep, and REM sleep. This is done by measuring heart rate and respiration rate, which vary depending on the sleep stage. For example, your heart rate lowers as you move into deeper sleep. However, it is important to note that watches cannot directly measure brain activity, so they cannot conclusively determine which stage of sleep you are in.

Additionally, some watches allow you to input lifestyle factors that can affect sleep quality, such as caffeine intake, stress levels, and eating habits. By tracking these factors, watches can help you identify patterns and make changes to improve your sleep. For example, you might find that you sleep better on days when you consume less caffeine or when your bedroom is cooler.

It is worth noting that while watch tracking can provide valuable insights into your sleep patterns, it is not a substitute for medical diagnosis. If you have concerns about your sleep quality, it is recommended to consult a health practitioner.

Sleep phases

Sleep is a complex and variable process that differs from person to person. The human body typically cycles through two main phases of sleep: rapid eye movement (REM) and non-rapid eye movement (NREM) sleep. NREM sleep is further divided into three stages, known as N1, N2, and N3, with N3 being the deepest stage characterised by slow-wave sleep (SWS) and delta waves.

The duration of each sleep stage can vary, and a person will usually go through four to six sleep cycles per night. Each sleep cycle lasts around 90 to 110 minutes. During a typical night, an individual cycles through various stages of sleep, from light sleep in the initial stages to deeper sleep in the latter stages.

REM sleep is the final stage of the sleep cycle, characterised by increased brain activity, dreaming, and the processing of information and long-term memory formation. As sleep progresses, REM cycles increase in length. While sleep trackers can provide insights into sleep habits, they do not directly measure sleep. Instead, they often estimate sleep by detecting periods of inactivity.

Smartwatches and fitness trackers can monitor certain physiological parameters to provide insights into sleep patterns and phases. These devices can track heart rate, respiratory rate, movement, and pulse, which tend to slow down as an individual reaches deeper stages of sleep. Additionally, some watches have an accelerometer and a microphone to detect movement and breathing patterns. However, these devices cannot conclusively determine which stage of sleep an individual is in, as that would require direct brain wave monitoring.

Sleep environment

Sleep trackers can help you understand your sleep patterns and the quality of your sleep. They can also help you recognise patterns in your sleep habits. For example, you might feel more sluggish sleeping from 10 pm to 6 am, but more energetic when you sleep from 11 pm to 7 am. You might also sleep better when your bedroom is cooler or on days you exercise.

Some sleep trackers can also record the environment of your sleep and how comforting it is. For example, some trackers use a microphone to capture noise from the room or your body. If you're moving frequently and not sleeping well, some trackers will note that. A microphone can also measure your respiration, detecting snoring, sleep apnea, and how often you wake up during the night. Some sleep trackers with thermometers can measure the temperature of your room and may show that you wake up frequently when it's too warm.

Sleep trackers can also prompt you to enter information about activities that can affect your sleep, such as how much caffeine you've had, when you've eaten, or whether your stress levels are high.

If you're concerned about the quality of your sleep, it's a good idea to talk to a health practitioner. If you're healthy and just want to gain some insight into your sleep routine, tracking devices might be a good option. However, it's important to remember that tracking your sleep doesn't necessarily result in better sleep. Changing habits based on what you learn is key.

Frequently asked questions