The study also found that among patients who reported perfect health, there was a higher percentage of normal sleepers -- those who get 6 to 9 hours of sleep each night -- who had significantly lower scores for depression severity compared with short and long sleepers with perfect health.
Short sleep was defined as less than 6 hours per night and long sleep was classified as more than 9 hours per night.
Dr. Charles Bae, a neurologist at the Cleveland Clinic Sleep Disorders Center, and colleagues analyzed data from 10,654 patient records collected from January 2008 to May 2010. The patients had a mean age of about age 52.
"It was surprising to see that sleeping less than 6 hours and more than 9 hours is associated with a similar decrease in quality of life and increase in depressive symptoms," Bae, the principal investigator, says in a statement. "I thought that there would be changes in quality of life and degree of depressive symptoms for short and long sleepers, but did not expect that those changes would be similar in both groups."
The findings were presented at the 25th Anniversary Meeting of the Associated Professional Sleep Societies LLC in Minneapolis.