Say your alarm clock rings in the morning and you wake up unrefreshed. Did you go to bed too late? Are you simply a night owl? Would it have been better if the alarm had gone off 10 minutes earlier and didn't interrupt your dream?
Developers of sleep tracker apps for smartphones say the programs can answer questions like these and help you to sleep more soundly.
But do they really? A closer look shows that some apps can do more than others.
The simplest is the pre-installed iPhone Clock app in iOS 10, which has a Bedtime tab. The app reminds the user when it's time to go to bed and measures sleep duration.
The ad-funded Sleep Better (iOS
) app and the Sleep Cycle alarm clock (iOS
) app also monitor movement during sleep as well as the effects of factors such as exercise, stress and diet. Sleep Better also provides a place to keep a dream journal.
"You're supposed to put the smartphone beside your pillow," explains tech reporter Julia Struck. "By monitoring movement of the mattress, the app assesses the quality of your sleep." It does this via the smartphone's accelerometer – in airplane mode as well, which many users switch to at night so as to sleep undisturbed.
In addition to monitoring movement, apps such as SnoreLab (iOS
) and Pillow (iOS
) track bedroom noise to let users know if they snore, talk in their sleep or sleep less soundly if it's noisy in the house or outside.
When users get up in the morning, the apps show detailed movement and sound graphs so that users can see whether there's a link between noise and movement during sleep.
If you regularly use a sleep tracker app for a substantial period of time, you'll definitely learn more about your sleep habits and how your daily routine affects your sleep. Do you sleep worse after a stressful day, and better after a glass of red wine or a long walk?
Dr Ingo Fietze, director of the Sleep Medicine Centre at Charite university hospital in Berlin, says apps that make people more aware of how they sleep are a good thing. "You should sleep an average of 7.5 hours a day," he remarks. "Using these apps, you monitor your sleep duration and can see at the end of the week whether you got your target amount."
Fietze adds, however, that using a sleep tracker app isn't comparable to an examination in a sleep laboratory, which also measures brain and muscle activity, along with eye movements, during sleep.
A feature that seems to be especially popular and is found on almost all sleep tracker apps is a "smart alarm". It doesn't wake up the user at a specific time, but instead during his or her lightest sleep phase within a 30-minute window that ends at the user's set alarm time. The feature's developers claim that it helps the user wake up feeling well-rested.
"The best way to start the day is undoubtedly to wake up on your own, refreshed," says Dr Alfred Wiater, president of the German Sleep Society. If you have to get up by a certain time though, a smart alarm is a good choice, he adds.
As for the efficacy of sleep tracker apps in combating sleep disorders, he warns that they were often inaccurate and could exacerbate the problem in some cases.
Struck brings up data privacy concerns. "If you use a smartphone sleep tracker app, you should be aware that the data are being collected," she says. "The app knows how much you move and how long you sleep," and it's unclear what happens to the data since "the providers often secure themselves extensive rights to them."
To use all of an app's features, you often have to register with your name, sex and birth date in addition to your email address.
The bottom line is that sleep tracker apps can familiarise you with your sleep behaviour and help you get more restful sleep – if you don't have chronic sleep problems. If you do, Fietze says, the apps are no substitute for medical treatment. "Persistently disturbed sleep calls for a sleep expert." – dpa