I've read some about this in the past. I wondered if the "two block pattern" noted by Western cultures in earlier centuries had anything to do with adrenal fatigue brought about poorer nutrition (possibly lowered B12 status, among other things).
For the past several months I've been making an effort to get up and out of my house every day between 7a and 9a, and spend at least a half hour outside. Luckily I live in a temperate, mild clime that allows me to do this year round. I think it most definitely has been paying off in the quality of my sleep. I'm consistently sleepy no later than 11p at night (so am in bed by then) and don't have much trouble with getting up or falling asleep during the day. I feel much better rested and have more energy.