It could be as important as the number of hours you sleep. 
Woman sleeping next to an alarm clock on bedside table
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When it comes to sleep, many of us have one goal in mind: get more of it. But new research suggests another factor might be just as important: what time you hit the hay.

To determine which sleep behaviors are the best predictors of cardiovascular health, researchers from the University of Delaware examined data from the UK Biobank Resource collected between 2006 and 2010. Their sample included 439,933 adults between the ages of 40 and 69. The results of the study are published in Annals of Behavioral Medicine.

Before conducting their analysis, the researchers identified short sleep as less than six hours, adequate sleep as seven to eight hours, and long sleep as nine hours or more. Each respondent was asked whether they considered themselves a morning person, more morning than evening, more evening than morning, or an evening person. Additionally, they were asked about their daily habits, including how much physical activity they did, how much time they spent using a computer or watching television, how many servings of fruits and veggies they ate, and how many cigarettes they smoked.

The results revealed that the participants whose sleep was either short or long and those who went to bed later were more likely than the adequate sleepers (clocking between seven and eight hours) and those who went to bed earlier to smoke, remain sedentary, and eat fewer fruits and vegetables. The findings are the latest in a number of studies that have linked later bedtimes to negative health effects.

“These data suggest that it’s not just sleep deprivation that relates to cardiovascular risk behaviors, but too much sleep can relate as well,” Freda Patterson, lead researcher of the study, said in a statement. “Oftentimes, health messages say we need to get more sleep, but this may be too simplistic. Going to bed earlier and getting adequate sleep was associated with better heart health behaviors.”

If you’re a night owl, don’t panic: here are some tips on winding down earlier.