World Sleep Data

What is the average bedtime, and how does it link to sunset? How does the average wake up time compare with local sunrise? Do these results vary for different parts of the world? How do you gather data for such a research project?

These were some of the questions posed by researchers at the University of Michigan in the Department of Mathematics and the Department of Computational Medicine and Bioinformatics. In an article published by Science Advances, they describe a smartphone app that they created: ENTRAIN. They made this app available for free to iOS and Android users; it makes suggestions about optimal lighting schedules when moving between time zones. The app also allows users to share their information about sleep and wake times, lighting data, and demographic information such as sex, age, and location. While it was a self-selecting sample, the researchers found that the data aligned well with other published sleep studies. They found that 18 to 19 year olds go to sleep earlier than 20 to 24 year olds, and that the start time for sleep starts to move earlier again around ages 50 to 60. The study also found other interesting results, such as the average bedtime is earlier and length of sleep is longer in the U.S. and Canada than in Japan or Brazil.

Perhaps the most interesting point about this study is the source of the data. By releasing a simple, useful app “into the wild,” the researchers were able to gather a significant amount of information. They received data from more than 8,000 subjects in the first year that the app was available. This is an interesting demonstration of the power of self-reported health information, and could be the harbinger of things to come as researchers take advantage of crowd-sourced data for other study questions.