Is “social jet lag” the reason why you’re tired all the time?

Chances are, you won’t make it through the day without hearing at least three people sigh these three little words: “I’m so tired.” Complaining about exhaustion has (sadly) become as common as talking about the weather or counting down until the weekend. But why exactly is everyone so beat in the first place? According to a new study published in the journal Sleep, it’s due to “social jet lag.”

Never heard of it? The term refers to everything that goes down during the weekend that messes up your snooze cycle—mostly, going out (or staying in) late with friends, then sleeping in the next morning. It’s not shocking that all of this can throw off your schedule during the week—but new research shows that it can also mess with your health in more serious ways than previously thought.

“A regular sleep schedule may be an effective, relatively simple, and inexpensive preventative treatment for heart disease as well as many other health problems.”

Each hour of social jet lag—AKA sleep lost during the week because of your weekend habits—can make you 11 percent more likely to develop heart disease, researchers found.

“These results indicate that sleep regularity, beyond sleep duration alone, plays a significant role in our health. This suggests that a regular sleep schedule may be an effective, relatively simple, and inexpensive preventative treatment for heart disease as well as many other health problems,” says Sierra B. Forbush, the study’s lead researcher.

So how much sleep should you aim for—on weekdays and weeknights? According to the American Academy of Sleep Medicine, seven hours. As if you needed another reason to forgo the bar and go to bed early on Friday night. On the plus side: That means more time to have the brunch of your dreams on Saturday morning. (Hello, matcha-spirulina donuts.)

Our editors have been putting themselves to the test for the cause of better zzz’s: Here’s what happened when they tried early-to-bed sleep training and a 9 p.m. digital curfew.