Do you wear a smartwatch to bed? If you do, you know that it tracks your sleep. It provides data on how long you slept, how long you spent in each stage of sleep, and how many times you woke up throughout the night. More sophisticated watches estimate blood oxygen saturation, snoring, sleeping heart rate, and restlessness. You’d think you could diagnose your own sleep disorder with all that information, but a doctor still needs to provide a diagnosis. Here’s why.
How Do Smart Watches Track Sleep?
There are different ways smartwatches track sleep depending on the brand, but there are five overarching ways: motion detector, heart rate, respiration, blood oxygen, and environmental factors.
An accelerometer is a small motion detector. There are multiple on your smartwatch, and as you sleep, it detects movements. It sends the data into an algorithm that estimates your sleep time and quality. These small motion detectors are how it tracks your steps and exercise, too.
Optical Heart Rate Sensor
The optical heart rate sensor is used for many different tracking purposes on your smartwatch, but it also tracks your heart rate while you sleep. Heart rate can vary when sleeping, but it tends to correlate with different sleep stages.
This sensor also plays a role in tracking your respiration. Your automatic nervous system plays a role in regulating your respiration, which helps determine your sleep stage. Respiration is an essential piece of data because it could indicate a sleep disorder when monitored by a doctor.
Some smartwatches have a microphone that detects sounds, restlessness, and respiration. This helps the watch determine if you snore, move around a lot, or labored breathing.
Have you seen the light on the inside of your smartwatch? That is the reflectance oximeter. It senses your blood oxygen saturation from the reflection of your blood through your skin.