Review of Sleep Cycle App: Tracking Movement to Time Awakenings

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?

Sleep Cycle relies on your smartphone's accelerometer to monitor movement. The idea is that you place your smartphone 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 four tabs of controls and information for the iPhone version: Alarm, Statistics, Trends, and Settings. There are 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 on the Statistics page that includes a hypnogram (showing sleep stages) as well as your bedtime, wake time, and total and average sleep time.

The Trends tab will let you review your sleep quality for various periods (days, weeks, and months). It even offers comparison to others in your country (as well as the countries with the lowest and highest sleep qualities). There are many graphs, tracking:

• Sleep quality
• Time went to bed
• Time in bed
• Time woke up
• Snore
• Increased sleep quality
• Decreased sleep quality
• Sleep quality affected by air pressures
• Sleep quality affected by the moon
• Activity (steps)
• Sleep quality affected by activity (steps)
• Heart rate (bpm)
• Sleep quality per day of the week
• Time in bed per day of the week
• Overview (total nights, total time in bed, average time in bed, shortest night, longest night, best night, and worst night)

There are also options to share this information by email, Twitter, and Facebook.

There are additional features that are unlocked and available with the Premium version, including:

• Online backup
• Sleep aid (emits a soothing sound to help you fall asleep)
• Sleep notes (help you track how different activities, such as drinking coffee or working out, affect your sleep quality)
• Wake up mood (prompted upon awakening and saved)
• Weather (shows today's weather upon awakening)
• Heart rate (uses color changes in the tip of your finger to measure)
• AirPlay (alarm sound can play through Airplay speakers)
• Philips Hue (can use your linked lights to wake you)
• RunKeeper (connects to the app to track activity)

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 (though this risk is admittedly low).
• The accelerometer will pick up any movements, including potentially those of bed partners or pets.
• It brings your phone into the bedroom, and unless you put the phone in airplane mode, you may 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.

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, which give it a limited utility, and I would not recommend it for these reasons.