Review of 'Sleep Cycle' App, Tracks Movement to Time Awakenings

An alarm clock keeps time. Getty Images

One of the most popular of the sleep-related apps (or applications) for iPhone, 'Sleep Cycle' works by tracking your movements during the night in order to perfectly time your morning awakening. What are the pros and cons of this app?

How it Works

'Sleep Cycle' relies on your iPhone's accelerometer to monitor movement. The idea is that you place your iPhone near you in bed and that it will register movements. When you are in deeper sleep, especially REM sleep, it will document this stillness. When you are restless towards morning, drifting into lighter stages of sleep, it will seize on this wakefulness to alert you to get up for the day.

The interface of the app is slick. There are five tabs of controls and information. The first tab offers instructions on how best to place your phone and use the app. Under settings, you can choose an alarm sound (including a favorite song) and set your snooze options. You select a 30-minute period that you wish to awaken during. Then, each night after using it, it creates a summary page that includes a hypnogram (showing sleep stages) as well as your bedtime, wake time, and total and average sleep time. There are also options to share this information by email and Facebook.

'Sleep Cycle' is accurate at tracking the consistency of your sleep schedule. This is similar to documenting your sleep patterns with a sleep diary, and akin to monitoring that is better accomplished with an actigraph. But at a cost of just 99 cents, it is much less expensive than actigraphy.


There are unfortunately a lot of drawbacks to the 'Sleep Cycle' app:

  • In order to function, the program must run overnight and this will slowly drain your battery. Although it will no doubt vary with your battery's age, it drained mine by 20% over 8 hours. The instructions recommend that you keep your phone plugged in, which could present a choking hazard should you become wrapped in the cord.
  • The accelerometer will pick up any movements, including those of bed partners or pets.
  • It brings your phone into the bedroom, and unless you put the phone in flight mode, you will be bothered with calls, texts, and alerts throughout the night.
  • The sleep cycle hypnogram (for which the app is named) does not appear to be accurate. If you have a soft mattress pad or other bedding, the accuracy will suffer even more because movements will be missed.
  • Setting a 30-minute window in which to have my alarm go off often left me getting less sleep than I desired. I would pick the later time to be the time when I absolutely had to wake up. More often than not it would awaken me earlier, which left me with less sleep than I had desired. I never really felt that I awakened more refreshed because of the perfectly timed alarm clock.
  • In general, having the phone in bed also made me more conscious of being awake or asleep, and this seemed to fragment my sleep.

Therefore, though 'Sleep Cycle' is an exciting development in inexpensive technology that may help us to monitor our sleep, it seems that it is really only accurate to track your bedtime and wake time. It should not be used as an alternative to more sophisticated sleep studies. There are a lot of problems with its use, and I would not recommend it for these reasons.

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