Yes, some data with actigraphy would be very interesting. I guess in that case it would be difficult to follow 170K people over 4 years. Folks wearing fitness

Yes, some data with actigraphy would be very interesting. I guess in that case it would be difficult to follow 170K people over 4 years. Folks wearing fitness trackers have quantitative data over a long period of time. I have no idea how reliable those measurements are.