I’ve collected even more observations supporting the idea that outdoor light improves my sleep, as discussed earlier. Now I’d like to get some idea of the dose-response function. To sleep really well do I need two hours of outside light? Four hours? Eight hours?
I’ve started to rate my sleep on a scale where 50 = average sleep (average for the months before I started spending more time outside) and 100 = best sleep imaginable (which I got after standing about 10 hours). And I’ve started to use a stopwatch to measure how long I spend outdoors. I’ve also been using a light meter to measure the strength of light in various places. When I’m outdoors it’s almost always in the shade. Today I discovered that sitting indoors next to a cafe window the incident light was just as bright as when I sit outside. Great to know because indoors I can plug in my laptop.
A 1994 book chapter from Daniel Kripke‘s lab reported a correlation (0.24) between low light exposure and “abnormal sleep.” So the connection I am now studying has been plausible for many years. The measurements I am now making are easy, but no one made them. Perhaps too many people believe that anything other than a double-blind trial with control and experimental groups is, as Peter Norvig, Google’s Director of Research, believes, a “mistake.”