Scientific studies can go one of two ways: They can prove a correlation that's totally awesome and life-affirming, or they can tell you that you're doing everything wrong and will die probably early. (They can also be completely bogus or misinterpreted, but that's beside the point.) For instance, just when you thought sleeping in was a good thing, science has come along to ruin your day.

It turns out that, although deviating from a habitual sleep schedule might still mean you're more creative than the average person, oversleeping is actually terrible for you. A new study from the University of Sydney in Australia links increased longer sleeping times to increased mortality rates—in other words the more you sleep, the sooner you die. In fact, sleeping more than 9 hours a day increases your mortality risk by 31 percent. Bummer.

The study surveyed more than 200,000 people age 45 and older in New South Wales. It examined their daily habits over a six-year period, beginning in 2006. Professor Emmanuel Stamatakis, one of the study's authors, said the link between long sleeping periods and death might not be direct. "One possible explanation is reverse causality," he said. "Long sleeping times could be indicative of an underlying undiagnosed disease."

It's also possible that, although people reported long sleeping times, their sleep quality was poor. "In the survey people were asked 'How long did you sleep?," Stamatakis said. "This most likely elicits an answer to the question: 'How long were you in bed?' This says nothing about the quality of the sleep, so reported long sleep duration could in fact be indicative of fragmented, restless and poor-quality sleep." And poor sleep is connected to increased rates of mortality.

In short, you should be more worried about the quality of sleep you're getting than the quantity. If your sleep is consistently interrupted or if you can't fall asleep in the first place, you're more likely to have something seriously wrong with you, which could lead to an early death. Sweet dreams!