Quantified Health. Part 3: Measuring Sleep
Thomas Bekker once said: “Sleep is the golden chain that ties health and our bodies together”. The quality of sleep is one of the principal indicators of peron’s health, both mental and physical, and I have been tracking it for awhile now, using the following several approaches: subjective assessment scale, Bodymedia tracker, and Sleep Time app.
The first thing I do after I get out of bed is to answer these three questions, using 10-point scale:
(1) How restful was you sleep?” (1 = “Not at All”, 10 = “Very Restful”
(2) How content are you with the length of your sleep? (1 = “Not at All”, 10 = “Very Content”)
(3) Overall, how satisfied are you with the sleep? (1 = “Not at All”, 10 = “Very Satisfied”
The arithmetic average of responses to all three question is my subjective indicator of that night’s sleep.It ranges between 6 and 8, and my ultimate goal is to increase it to 8 or 9:
- sleep duration,
- sleep “efficiency” (sleep time as % of total time in bed)
- sleep interruptions (number of times I woke up during the night)
- sleep “inefficiency” (my personal metric, computed as total time up as a result of interruptions, as % of total sleep time).
For example, on July 16, readings from my Body Media were:
Time Sleeping = 6 hrs 21 min (381 min)
Time Lying Down = 7 hrs 11 min (431 min)
Sleep Efficiency = Time Sleeping/Time Lying Down = 381/431 = 88.4%
Further examination of the sleep chart reveals that my sleep was interrupted 9 times, and during these breaks I stayed for approximately 41 minutes. Thus,
Sleep Interruptions = 9
Sleep Inefficiency = 41/381 = 10.8%
My ultimate goal is to increase the sleep efficiency to 95%, reduce the number of sleep interruptions to 3-4, and lower sleep inefficiency to 5%.
The second set of readings come from the Sleep Time app by Azumio that also doubles as an alarm clock.
The Sleep time provides me with the estimates for REM+Deep and Light sleep time, and calculates the sleep efficiency in the same manner as Body Media. It also serves me as an intelligent alarm clock: I set the desired target time to wake up and place my phone on the mattress next to me right before going to sleep. The app uses iphone’s accelerometer to monitor my movements and identify the best time to activate the alarm. I think it uses the increased frequency of movement as a cue that I am in the “light” stage of sleep, and can be awaken.
As soon as I accumulate enough data points, I plan to look at the correlations between all the sleep quality metrics mentioned above. In a couple of weeks, I also plan to launch my first “sleep hack” experiment to investigate empirically if herbal supplements can improve the quality of my sleep. Stay tuned!