[crich70]

Actually our sleep patterns are probably out of sync more due to the electric light than an ereader I'd think. Prior to the electric light being so easily acquired people went to bed shortly after it got dark as oil and kerosene lamps were expensive to keep going late into the night. And the natural sleep pattern (as I understand it) is to have 1st sleep and 2nd sleep. 1st sleep goes from when people would go to bed til around midnight. Back in the day when people woke from 1st sleep the mother of the family would check in on the kids or other short term tasks while the man of the house would take care of anything (on the farm) that he hadn't earlier in the day (maybe some milking etc) and it was also the time when a lot of babies would be conceived as people were rested (and any children in the house were asleep). Then people would go back to sleep til it was time to get up. Now days though we tend to stay up later and don't get enough sleep on top of it. Plus we are temperature sensitive. If we are too warm or cold it throws our biochemistry off and we wake up groggy and unrested.