There was an interesting programme on the nature of things. They made an argument that blue light at an inappropriate hour destroys our melathonin needed for a good night sleep.
http://www.cbc.ca/natureofthings/episode/lights-out.html
The video says only available in Canada (cheap of our CBC)but perhaps our American friends will be able to access the text and comments.
There was an American scientist that this phenomena causes a substantial increase in breast cancer and it is being blamed for the growing amount of obesity. You wonder if this hormonal disruption has something to do with the increasing popularity of diabetes.