Statistics say: most people in developed countries have problems with the quality and duration of sleep. We need good sleep for our health. Today we can use sleep trackers that seem to help solve these problems, and manufacturers confidently report that a fitness bracelet and its program will help improve the quality of sleep. How about really? We will find out the opinion of experts about these devices: to whom they help, for whom they are useless, and how they can harm even a healthy person.
How does sleep work?
Sleep quality is based on sleep-wake cycles, non-REM (deep) sleep and REM sleep.
During deep sleep, the body is relaxed, breathing is rhythmic and calm, pressure decreases, the brain reacts less to external stimuli. Slow sleep is the optimal phase for recuperation, and also for the production of growth hormones by the pineal gland, which helps to renew and regenerate tissues, and restore immunity.
REM sleep helps the brain more: unnecessary information is erased, the necessary information is analyzed, transferred to long-term memory, and the number of neural connections increases. At the same time, body temperature rises, blood pressure rises, and the heart rate increases. And the body moves. The REM phase is observed 3–5 times per night.
We need both phases: in the slow phase, physical health is restored, during the fast phase, mental abilities are restored. Accordingly, if the quantity and/or quality of the phases is disturbed, health suffers.
The ancestor of fitness bracelets with trackers: how it all began
It seems that everything sounds simple: to recognize the phase of sleep, you just need to track your heartbeat, temperature and body movements. The task is just for a fitness bracelet!
The principle of evaluation for trackers is copied from the actigraph, a motion sensor designed at the end of the last century. It was the first “sleep tracker” that allowed tracking sleep and wake cycles, that is, it helped scientists determine whether the patient was sleeping or not. Some models even claimed to determine sleep phases. And in order to trust the testimony of actigraphers, they were compared with the results of polysomnography.
A polysomnograph is a device, or rather, a set of devices in a specially equipped room. A person sleeps in it, and the devices track literally everything: EEG readings, small movements of the eyes under closed eyelids, chin muscles, and heart rate indicators. This “gold standard” of sleep research really allows you to determine not only cycles, but also phases.
Actigraph vs. tracker bracelet
When actigraphs (which are the size of wristwatches) were introduced, somnologists naturally compared their readings with polysomnograph data. And they found that scientific actigraphs are able to determine whether the patient was sleeping or not. And with a fairly high accuracy — 90% — determine whether he woke up at night. And they are not very suitable for determining the phase of sleep, which is why patients with serious problems are still prescribed a polysomnographic study, leaving them overnight in a special room. That is, even an actigraph, a medical device that has passed the data validation process, will not determine the phase of sleep.
But modern gadgets are multifunctional and, it seems, can do everything. They will appreciate the quality of sleep, and wake up at the right time. The idea on the basis of which such trackers are developed is, in fact, scientific. But with the confirmation of the data that the trackers receive and process, a problem arises: not one of such popular devices has been validated by scientific research methods. No company has conducted sleep studies and compared their results with trackers. That is, bracelets work based on algorithms written by software developers based on some general data. “Move a little — fast sleep, move a lot — woke up”, something like this.
Neil Segal, Senior Fellow, Center for Digital Health Innovation, USA
After two years of comparing data from consumer gadgets with results from clinical medicine research, we concluded that very few devices can be compared to real medical devices. The FDA rates sleep trackers as “health-focused devices,” which means the consumer gets more information about their health. Which? Doctors don’t understand this yet. Such trackers are based on a good idea, but there is no evidence that it works. In general, some gadgets help people to be more active or attentive to themselves, but these are the only bonuses that we have found so far.
Same story with the “wake up on time” option. We know that it is better to get up in the phase of REM sleep, which is with dreams. In this phase, a person has a so-called low awakening threshold, it is easier to get up, the body is “warmed up”, the brain reacts faster. This phase is perfectly tracked by the polysomnograph in terms of EEG and eye movements. Actigraph and trackers can only track external indications, changes in the intensity of movements, possibly heartbeats and sounds (depending on the device). The tracker monitors the number of changes in its position and heart rate and decides that the fast phase has come. Then it takes into account when, according to its data, the person fell asleep. If more than 7 hours have passed, you can wake up the owner.
The problem is still the same: there is no confirmation of effectiveness, even scientific actigraphers cannot cope with the exact determination of the sleep phase, what can we say about fashionable gadgets?
Sleep trackers that show changes in body position and record sounds can really help people with somnambulism or snoring to tell if there was a sleepwalking episode at night, or how long and how often sleep apnea episodes occur. This is a good option for collecting information for the doctor.
Many knowledge — many sorrows
The number of indicators that sleep trackers provide is also, oddly enough, a problem. Even if we do not take into account their reliability, it turns out that these data will not help doctors in any way. Or almost nothing. Experts refer to these data as “raw”: their use requires medical knowledge at the level of a somnologist. And the doctor will again return to the question of the error of the collected information.
Mikhail Poluektov, sleep medicine doctor, head of the sleep medicine department, PMSMU. I. M. Sechenov, claims that the array of data received from the tracker can provide information about the daily routine. If a complaint is received that the patient does not sleep well, and the tracker shows that on Friday he fell asleep at 3 am, on Saturday at 5 am, and on Sunday at 11 pm, then this is a violation of simple rules. But do you need a tracker for this? Although these data help a lot in assessing the quality of sleep of the elderly, who “can’t fall asleep at night”, because they have already slept twice in the morning and in the afternoon, but they don’t want to admit it.
That is, all information from the tracker is general, and the interpretation of its value in relation to sleep quality is of low value. And it is impossible to prescribe treatment on its basis, except to give recommendations on restoring the daily routine.
Useless or harmful?
So far, we’ve learned that sleep trackers are actually of little use. Tables, graphs and various indicators may not correspond to reality, and their information content for the doctor is rather low. What’s wrong with trackers?
Trackers and the programs they use to track everything are based on ideal ideas about how a person sleeps. That is, it is based on the average data of polysomnographic studies, which seem to be suitable for all people. And immediately there are two difficulties:
a tracker, even a scientific actigrapher, is not a polysomnograph, and it cannot track all indicators, no matter what advertising claims;
we are all different. And each of us not only differs from another person in needs and sleep rates, but also changes with age. For example, Donald Trump at 71 years old needs 4–5 hours of sleep for full health, and this is confirmed by a polysomnograph. And in almost every person by the age of 80, the duration of the REM phase is reduced by more than half. This is also the norm.
Surprisingly, the most frequent complaints of sleep trackers owners are not about the quality of sleep, but about the performance of the device. He seemed to sleep well, but on the screen — only 1.5% of the REM phase (REM sleep) per night! It’s not healthy sleep at all, is it?
It would seem, what is the problem? If I slept well, let the device say anything. I know that I slept well and was awake, didn’t I? It turns out that we tend to trust the “scientific” indications of bracelets more than our own well-being. So, in one experiment, people with significantly good sleep in the morning were told that they slept badly today. And this significantly affected both well-being and daytime activity: the participants themselves reported that sleep was restless, intermittent and did not bring rest.
So in theory, tracking sleep quality is useful: you can learn more about your body. But in practice, we lack skepticism: trust in the numbers on the screen is higher than in your body. And this is the biggest trap of sleep trackers!
Orthosomnia is a condition where a person is so preoccupied with the question of whether he sleeps well enough and for a long time that real problems with sleep begin. For example, someone begins to worry about sleeping more time in bed without sleep (which somnologists do not approve of). And the readings of the instruments in the morning determine the state of health for the whole day, a real obsession with the quality of sleep begins. If we add to this the imperfection of tracker indicators, one can easily imagine what kind of neurosis can be “earned” in this way.
Fitness bracelets with trackers are not medical equipment. They are useful in diagnosing sleep apnea, somnambulism, restless sleep, and tracking the results of therapy. But hope for other indications and their significance for health is not worth it. The only reliable assessment of the quality of sleep is based on indicators of brain activity, and not on the external manifestations available to popular gadgets.