Is it reliable to use smart bracelets to monitor sleep?

This is the 4038th article of Da Yi Xiao Hu

The "China Sleep Research Report (2022)" shows that in the past 10 years, the Chinese people have fallen asleep more than 2 hours later, and the average sleep time has been reduced from 8.5 hours in 2012 to 7.06 hours in 2021. Only 35% of Chinese people sleep for 8 hours. The factors that affect sleep duration are: watching mobile phones or surfing the Internet leads to delayed sleep, and work or study takes up sleep time. More than half of the people think they have sleep problems, including dreaming and shallow sleep. Many people choose to use portable devices such as smart bracelets and watches and various sleep apps to monitor their sleep status.

Wear a smart bracelet to sleep, and when you wake up the next day, the data will tell you the "deep sleep time" and "light sleep time" of that night. You often feel anxious because of the short deep sleep time... Are these monitoring data really reliable?

The standard sleep monitoring equipment is "polysomnography", which is a non-invasive examination that can record multiple signals of sleep status throughout the night, including EEG, EOG, oral and nasal breathing airflow, snoring, mandibular electromyography, ECG, chest and abdominal breathing, upper and lower limb electromyography, etc. The instrument automatically analyzes it and then verifies it manually item by item in order to conduct a comprehensive analysis of the structure and process of sleep and the clinical results, thereby providing an objective basis for the diagnosis, classification and differential diagnosis of sleep disorders, and also providing important reference information for the selection of treatment methods and evaluation of treatment effects. It is currently the most authoritative sleep monitoring method and the "gold standard" for the diagnosis of sleep disorders.

The principle of the smart bracelet currently on the market is based on the fact that:

There is less limb activity during sleep and more activity when awake. Sensors are used to monitor several simple indicators such as body position, breathing, heart rate, blood oxygen saturation, etc. to infer the user's sleep condition. Therefore, the data recording the total sleep time is reliable.

However, for indicators such as "deep sleep" and "light sleep", since smart bracelets do not currently have the function of monitoring brain waves and eye movements, the sleep monitoring data calculated based on body movements or heart rate can only be used as a reference, and the results are of course different from the standard polysomnography results. Especially for the stages of sleep, smart bracelets are not accurate in judging "deep sleep" and "light sleep".

Therefore, if you are using or planning to use a smart bracelet to monitor your sleep, the focus should be on the total sleep time. You don’t have to pay too much attention to the so-called “deep sleep time”, “light sleep time”, “sleep score” and other sleep stage results displayed in the bracelet monitoring data. If the bracelet data aggravates your anxiety about sleep, then turn off the sleep monitoring function of the bracelet first and think about it: Is it because you didn’t sleep well before you started monitoring? Or did you “discover” that you didn’t sleep well after you started monitoring?

How long is the right amount of sleep per day? Is there a standard?

The latest research suggests the required sleep time for people of different ages: newborns should sleep 14 to 17 hours a day, adults should sleep 7 to 9 hours a day, and the elderly over 65 years old can sleep 7 to 8 hours a day. However, sleep time varies from person to person, and the quality of sleep should also be judged in combination with the individual's mental state and physical strength the next day.

Author: Yueyang Hospital of Integrated Traditional Chinese and Western Medicine affiliated to Shanghai University of Traditional Chinese Medicine

Shi YangDeputy Chief Physician

The author's clinic time: Saturday afternoon (Clinic Room 7, 4th Floor, South Building, No. 44 Qinghai Road)