Sleep trackers are designed to help us get a good night's sleep. Both fitness trackers and smartwatches offer functions to monitor sleep. However, incorrect use of the devices and data can trigger sleeping sickness instead of preventing it. I have been able to improve my own sleep with sleep tracking – and that must be taken into account.

Why sleep tracking?

One thing in advance: if you are satisfied with your sleep, you should forego sleep tracking. I explain why below. And if you have serious sleep disorders, please see a doctor. Sleep tracking with gadgets such as fitness trackers, smartwatches and cell phones is something for people who are curious about their sleep and who might want to optimize it a little. However, it is not a medicinal application .

In any case, I felt the need to learn more about my sleep. Sometimes I just wake up at three or five o'clock. Sometimes I have nightmares, sometimes I can't sleep. Sometimes I sleep too long or too short. In other words, I have a statistically relatively normal sleep – because nobody sleeps perfectly . Accordingly, many people are dissatisfied with their sleep without immediately having an illness. However, a higher quality of sleep is possible. Does sleep tracking help?

The limits and dangers of sleep tracking

While you don't need a gadget for counting steps and the cell phone is sufficient, in my opinion it looks different with sleep tracking. I recommend a smartwatch or a fitness tracker with a pulse sensor and blood oxygen meter . But remember: According to sleep researcher Dr. Günter Weeß made sleep unreliable .

Fitness trackers and smartwatches therefore show a deep sleep phase that is far too long, cannot recognize sleep phases such as REM sleep or deep sleep properly, and do not even differentiate between "lying awake in bed" and sleeping. I can confirm that when using my Fossil Gen 6, at least a current high-end smartwatch. The only reliable way to measure sleep is to visit the sleep laboratory , which is medically prescribed as a last resort. Among other things, brain waves are recorded there. However, I'm not nearly as sleepless as Al Pacino in the thriller "Insomnia". So that would be completely exaggerated for me.

If you go wrong with sleep tracking with the gadgets, it could even be that you are seriously imagining that you have sleeping sickness – or that you don't have one, even though you have one. In addition, you may not be able to fall asleep precisely because you are constantly worried whether your smartwatch will indicate a healthy sleep this time. In fact, sleep tracking can contribute to the obsessive quest for perfect sleep – which is itself a sleeping sickness called orthosomnia. Therefore, it is not recommended for people who are completely satisfied with their sleep.

Monitor sleep for less worry

So let's take it easy. Despite the shortcomings and limitations, I found sleep tracking to be very useful : I had previously thought about whether I could have sleep apnea and perhaps one day would not wake up at all for no good reason – the usual men's worries. The blood oxygen sensor of the smartwatch told me, however, that the oxygen percentage only very rarely suddenly decreases during sleep and that only slightly to an uncritical level. The other data also suggest that everything is OK. So I can calmly imagine another illness.

And this is how sleep tracking works : I use the Sleep as Android app on my Samsung Galaxy Note 9 to evaluate the sleep data. I connected it to the Fossil Gen 6 and included the sensor data from there in the evaluation. I use motion sensors for (unreliable) determination of sleep phases, sound recordings to record snoring, a pulse sensor and a blood oxygen sensor.

The next day I compare the abnormalities detected by a sensor with the results of other measurements . It was comforting to learn that I don't suddenly stop breathing while sleeping – that would be a sign of sleep apnea – only snoring. That was revealed by the sound recordings with the smartphone at the latest.

Fortunately, the pulse also speaks against sleeping sickness. He is a little below the resting heart rate, which he should. According to Sleep as Android, my "deep sleep" is far too long at around four hours – but luckily the information is incorrect because sleep trackers cannot correctly identify the sleep phases. Nevertheless, experience has shown that the information on "deep sleep" is helpful , I am more rested on days with more of it.

This is how sleep tracking helped me

Sleep tracking is therefore useful for allaying fears. It is also useful that the smartwatch and mobile phone remind me to always go to sleep at the same time. Tracking invites experimentation , as there are certain individual differences in the factors that contribute to healthy sleep.

I've found that I sleep particularly well if I do weight training a few hours beforehand. Although going for a walk is often recommended, exercising more power brings me more, but not right before bed. I shouldn't drink coffee in the evening, eat a lot, gamble or watch TV for too long. Even before tracking, I noticed how important it is to have a suitable mattress. Some questions remain unanswered, which I get to the bottom of with my mountains of data .

Conclusion: sleep tracking is useful – if you take it easy

Sleep tracking is like a detective game . It invites you to look into sleep and find out the factors that affect sleep. But it doesn't do that by itself. It works quite well when you know that the data from smartwatch, cell phone and fitness tracker are rather vague clues. However, I fear that some users will take the integers and charts at face value and not know what to conclude from them.

Even the "New York Times" editor Brian X. Chen could not draw any conclusions from his sleep tracking measurement results . And the trackers usually do not reveal what to do if the data suggests an unhealthy sleep – although some apps such as Sleep as Android provide useful information (albeit in English). It took a lot of additional research so that I could improve my sleep quality with the right measures.

I would like the manufacturers of smartwatches and fitness trackers as well as the providers of sleep tracking apps to be a little more cautious with their claims. When you understand what sleep tracking can and cannot do, it is fine and useful for experimenting and improving your own sleep. But if you take the data too seriously and strive for a perfect sleep, you could use the tracking to create the sleep problems that you wanted to avoid. I can recommend it to informed users such as the readers of this article if necessary.