TUESDAY, June 14 (HealthDay News) -- People who get six to nine hours of sleep each night rate their quality of life higher and are less likely to feel depressed than those who sleep less, according to a new study.

But, sleeping more than nine hours each night is ill-advised, the researchers found.

The study examined the records of 10,654 patients, who were about age 52 on average, over a two-year period. After accounting for differences in the participants' age, gender, race and marital status, researchers gathered information on their quality of life, feelings of depression and sleep duration.

Among the findings, slated for presentation Tuesday at a meeting of the Associated Professional Sleep Societies in Minneapolis, those with a "normal" night's sleep of six to nine hours reported high scores for quality of life and lower scores for depression severity, compared to short sleepers (fewer than six hours of sleep) and long sleepers (more than nine hours of sleep).

"These results are important because they provide more information about the importance of getting enough sleep, which is usually six to nine hours per night," the study's principal investigator, Dr. Charles Bae, neurologist at the Cleveland Clinic Sleep Disorders Center in Ohio, said in a news release from the American Academy of Sleep Medicine.

"People may already expect that their quality of life could be decreased when they do not get enough sleep, but they may not realize that sleeping too much can also have a negative impact," Bae said.

Although sleep needs vary from person to person, most people require seven to eight hours of sleep each night to feel alert and well-rested during the day, according to the news release.

Because the study is to be presented in a meeting, the findings should be considered preliminary until published in a peer-reviewed journal.

More information

The National Sleep Foundation provides more on sleep and depression.