wakemate
Myth:
Sleep cycles are 90 minutes long. Sleeping in 90 minute increments will help you sleep efficiently and allow you to wake up feeling refreshed. [1] There’s even an app for that! [2]
Reality:
Sleep cycles are comprised of 5 stages; stages 1-4 and REM. While it is true the mean sleep cycle is 90 minutes, the range is actually 60 – 110 minutes. Journalistic enthusiasm seems to have glossed over the simple, but critical, fact that 90 minutes is only an average length. [3] Additionally, after the first few sleep cycles, that amount of time you spend in stages 3 and 4 decreases, while the time spent in stages 1, 2 and REM increases. [4]
Since it’s almost impossible to time your sleep cycles, sleeping in 90 minute increments does not ensure you will wake up refreshed. That is why waking up to a traditional alarm is like playing Russian Roulette with your early morning sanity. [5]
However, waking up at the end of a sleep cycle does help you sleep efficiently and wake up refreshed. It is just hard to do so without outside help…
How the WakeMate can help:
We built the WakeMate to adapt to the unpredictability of your sleep. The best way to achieve a better night’s rest is to monitor your sleeping patterns over the course of the night. The WakeMate monitors a person’s sleep cycles via Actigraphy, a well-respected scientific monitoring system that has been employed by sleep labs for decades. [6]
The graph above is a sneak preview of a feature we are currently working on aimed at helping you figure out how long to sleep. It gives you real data on your personal sleep cycles. The x-axis represents how long you have been asleep and the y-axis represents the likelihood you are in each stage of sleep for any given minute. We calculate this by analyzing your WakeMate sleep history. For example, 4 hours after I fall asleep there is a ~40% chance I will be in deep sleep and a ~20% chance I will be in light sleep.
From the data above, you can see that at 6:45 I switch from a deep sleep cycle to a light sleep cycle. The same thing also happens at 8:00. Therefore, in order to maximize the amount of deep sleep I experience and wake up at the end of a sleep cycle, I should sleep for 6 hours, 45 minutes or 8 hours.
To feel refreshed when your alarm goes off, the best times to wake-up are at the end of a sleep cycle or during “almost awake” points which occur during REM sleep. These “almost awake” points are certain moments during REM when your brain thinks you are awake even though you are actually dreaming. The WakeMate finds these points using Actigraphy by analyzing the frequency and amplitude of your movements. The WakeMate then sounds the alarm so the transition to wakefulness is smooth and the urge to smash your alarm clock is not as strong.
tl;dr: Even if sleeping in 90 minute increments is not a useful strategy, the WakeMate is here to ensure you get the most out of your sleep and wake up feeling refreshed.
[1] http://www.ehow.com/how_4501483_improve-sleep-quality-using-easy.html
[2] http://sleepyti.me
[3] http://www.glenrhodes.com/?p=132
[4] http://www.sleepeducation.com/Topic.aspx?id=6
[5] Tassi P., & Muzet, A. (2000). Sleep inertia. Sleep Medicine Reviews, 4, 341-353.
[6] http://en.wikipedia.org/wiki/Actigraphy
Awesome. I am psyched about this new feature!
Great post!!
Really useful. As a wakemate user, I appreciate that you keep improving the web interface with more suggestions and information such as that new feature, sounds awesome!
I have one question though: How does this compare to waking up in the best moment in the usual 20 minute interval?
To be more specific, consider the following scenario:
What would be the difference (in your example) between waking up at 6:45 (or 8:00) and waking up somewhere between 7:00-7:20 (letting wakemate find the best spot) ?
Thanks!
Interesting data. I can’t wait for the new features on the site!
P.S. you might want to look into better footnotes: http://daringfireball.net/2005/07/footnotes . Even PG’s terribly basic footnotes http://www.paulgraham.com/articles.html are at least links! It is pretty straightforward: HTML anchors with links to both the reference and the spot in the body where it is referenced…
Keep it up!
I’m sorry but the way your graph is done there is really little meaning to the intersection of the 2 curves. Hence, deducing that you should “sleep for 6 hours, 45 minutes or 8 hour” based on the intersection x-coordinate of those curves makes no-sense.
What you graph said is : The longer you have been sleeping, the higher the probability to be in light sleep. The rest is noise generated sleep-cycle random offset
@Xavier — The difference in sleep stages is definitely not noise generated. We use Actigraphy to classify what stage of sleep you are in. The graph also tells you there is a higher probability you will be in light sleep as time goes on as you mentioned.
I will write an explanation of how we classify sleep stages in the future so you will be able to understand how the graph is generated.
@Pablo — Letting the wakemate wake you up between 7:00 and 7:20 will still wake you up refreshed, but not as well as if you had woken up around 6:45 or 8:00.
I tried to leave a comment on a previous post about polyphasic sleep, but when I submitted it, I got a message saying comments were closed for that post.. weird.
Anyway, first: +1 for the polyphasic sleep support feature. Second, I was very disappointed the other night when I went to bed late, woke up early and then the Wakemate app told me it wouldn’t upload the data because it was less than 4 hours of data. Hence, I lost that night’s sleep data, which is really bad, because when I don’t get much sleep is probably the time when I want to optimize my bedtime the most, but if I can’t track those days, I can’t do anything about it.