where the writers are
Blue Light, Circadian Rhythm, and Sleep Quality

Sleep quality seems to be linked to alertness, depression, Alzheimer's, and other interesting facts of life (obesity, hypertension, etc.) that concern sleep-deprived adolescents, electronic-device-dependent college students, graveyard shift workers, the aging population, and spaceship crew members. http://hi-seas.org/?p=267  http://www.technologyreview.com/view/424563/astronauts-measure-sleep-in-...

How do we avoid sleep disorder when the LED lighting http://www.dailymail.co.uk/health/article-2329068/Terrible-nights-sleep-... of a computer keeps us awake at night?  There seems to be a software that compensates for this. http://en.wikipedia.org/wiki/F.lux  However, avoiding computer use for a couple of hours before going to bed and/or using the amber-colored goggles for an hour or two before going to bed may be a better solution for some people trying to get their good night's rest.  (Of course, I've known some people to work at a computer until they can't keep their eyes open and go to bed and get a good night's sleep that way.)

http://chriskresser.com/how-artificial-light-is-wrecking-your-sleep-and-...

Do people who catnap to catch up on lost sleep actually get enough quality sleep? How many hours should an adult sleep daily on the average?   8, 7, or 6 hours a day?  At least five hours a day of quality sleep supplemented by a quality half-hour cat nap  http://en.wikipedia.org/wiki/Power_nap  or a one-hour nap?  http://www.nih.gov/news/pr/jul2002/nimh-02.htm How much sleep is too much or too little? (7 seems to be the magic number according to the article that follows, but sleep requirement is personal and differs from one individual to another.)  http://www.sleepfoundation.org/article/how-sleep-works/how-much-sleep-do...

It's good to know that ''people actually do wake briefly quite frequently during a regular night of sleep."  http://www.cbsnews.com/8301-500368_162-57377791/could-sleep-problems-pre...

The Myth of the Eight Hour Sleep 

http://www.bbc.co.uk/news/magazine-16964783

In the early 1990s, psychiatrist Thomas Wehr conducted an experiment in which a group of people were plunged into darkness for 14 hours every day for a month. It took some time for their sleep to regulate but by the fourth week the subjects had settled into a very distinct sleeping pattern. They slept first for four hours, then woke for one or two hours before falling into a second four-hour sleep. Though sleep scientists were impressed by the study, among the general public the idea that we must sleep for eight consecutive hours persists. In 2001, historian Roger Ekirch of Virginia Tech published a seminal paper, drawn from 16 years of research, revealing a wealth of historical evidence that humans used to sleep in two distinct chunks...

http://en.wikipedia.org/wiki/Segmented_sleep

http://www.npr.org/2013/02/08/171486710/science-of-slumber-how-sleep-aff...

Some data on sleep patterns..  

http://actigraphy.respironics.com/downloads/ActogramReferenceSheet.pdf   (shows patterns of "normal" sleep (continuous sleep,) insomniac, Circadian disorder, etc.)