A recent study out of Northwestern University studied the effects of disruption to the circadian rhythm of mice and how this affects their fertility.
The female mice were mated with the males, then their circadian clock was disrupted. Some of the female group was given extra hours of daylight, while others had hours taken away. The group given extra hours of daylight, only about half produced litters. The group that had hours taken away, only approximately 20% produced litters. These were in comparison to the control group who had a steady 12 hours of daylight and 12 hours of night= 90% of this group produced litters. You can read all about the study here: http://www.foxnews.com/health/2012/05/24/daily-rhythm-disruptions-linked-to-fertility-problems/
This was quite interesting, because let’s be honest, most of us are running around for more than 12+ hours a day (I’m thinking more likely 18). While the study findings may not directly be able to link to human’s fertility, it is something to think about. More research today is showing sleep deprivation or poor sleep may lead to a higher risk of heart disease and diabetes (among others).
Read more about your circadian rhythm here: http://www.nigms.nih.gov/Education/Factsheet_CircadianRhythms.htm