Sleep Tracking: Looking at Sleep Cycle

As mentioned before, I’ve been using the fitbit, the Zeo, and Sleep Cycle all together for over a month now. Honestly, I like all three.

With the combined data, I’m getting a good picture of my sleep. However, most people are not going to be as gadget happy as I am, and will only go for one of these sleep trackers. Maybe two at the outside. So I’ve been trying to figure out which of the three I’d pick if I could only pick one. And the answer is: it depends…

Sleep Cycle

Sleep Cycle is the one I expect will be most commonly used, simply because of the price point. It costs .99 cents. That’s pretty damned hard to beat. However,  Sleep Cycle is the weakest of the three trackers.

(This is going to be long; skip to the bottom if you just want the bullet points).

To use it, you place your iPhone/iPod on your bed, much like in the picture above (plugged in), set the alarm, flip the screen face down and go to bed.

It uses the actigraph in the iPhone, which seems fairly good. What bothers me about Sleep Cycle, though, is pretty much what I said back in this post. It claims that it can tell what phase of sleep you’re in at any given time. There’s just no way for it to do that.

An actigraph measures motion. It can’t measure brain waves. It can’t measure breathing. It can’t measure oxygen saturation or body temperature. Therefore, all it can really tell you is how much you moved around in your sleep. From that data, you can extrapolate whether or not you had a night of good sleep. It can give you a general picture.

Yet Sleep Cycle, in the user interface, implies that it can tell you more. And that bothers me. It can tell me when I’m awake. That’s fine. But dreaming? Deep sleep? I can see how there would be correlations between movement and sleep phase, but in my understanding, that isn’t conclusive enough to say, “Yes, you are dreaming now.”

From the graph, it looks like Sleep Cycle is just assuming that you spend a certain amount of dream time between deep sleep and waking. So, really, that’s just the slope between those two stages. That doesn’t seem particularly precise.

Aside from that, with Sleep Cycle you’re actually monitoring how much your mattress moves. The theory is that movements in the mattress reflect your movements. And that’s pretty imprecise as well. Mattresses vary.

For example, we have a waterbed. The mattress moves a lot. Even when I’m not the one moving it. My boyfriend moves, and Sleep Cycle registers it. When I sleep in our guest bed, a futon, the mattress barely reflects any movement at all. You can calibrate it for each mattress you sleep on, but even then it’s not going to be as accurate as something actually physically on you (like the fitbit).

It has an alarm clock function, that should wake you at the optimal moment in your sleep cycle. Great idea. When it works, it’s very effective. But it doesn’t always work. It went off this morning, waking me at an okay point but hitting my boyfriend at the worst point in his sleep cycle. I should note, we place it in between our pillows, so it’s in the middle of the bed and registers movement from both of us in the hopes of avoiding just such a situation. Oops.

On the other hand, it can be very useful to know how you and your partner affect each others’ sleep, and Sleep Cycle will help you figure that out.

• Affordable for iPhone/iPod users at .99 cents
• Fairly accurate actigraphy
• Gives a good general picture of your sleep
• For couples – gives a good picture of your sleep when you’re in the same bed

Cons

• Very expensive if you don’t have an iPhone/iPod (add the cost of the device)
• Somewhat misleading user interface
• Accuracy is variable dependent on mattress
• Not good for individual tracking in a shared bed

Conclusion:

It is a good tracker. It’s good for giving an overall picture, but it can’t deliver on what it promises. For .99 cents… you can’t really complain. If you already have an iPhone or iPod for other reasons, you should absolutely get it.

If you don’t have either of those devices, then suddenly Sleep Cycle goes from being the cheapest sleep tracker of the three to the most expensive. And that’s a different story all together. It’s not worth it at that price.

This is running a bit long, so I’ll stop here and post more later.