Sleep on this.

People who go to bed and wake up later on weekends than they do on weekdays may be harming their health, according to a study presented at SLEEP, the 31st annual meeting of the Associated Professional Sleep Societies. Indeed, so-called “social jet lag” is associated with worse mood, fatigue, and perhaps most disturbingly an 11% increase in the likelihood of heart disease, the research shows.

“These results indicate that sleep regularity, beyond sleep duration alone, plays a significant role in our health,” said lead author Sierra Forbush of the University of Arizona in Tucson. The study asked nearly 1,000 adults ages of 22 and 60 years about the timing of their sleep, as well as their health issues.

While this research didn’t show exactly why this happened, other studies have clues. Research has shown that disruption of circadian rythms has been associated with a number of problems, including hormanal fluctuations and cardiovascular and gartrointestinal issues  — and at least one researcher thinks some of this may have to do with how circadian irregularities mess with gut bacteria.

Whatever the reasons, there is one big takeaway: A “regular sleep schedule may be an effective, relatively simple, and inexpensive preventative treatment for heart disease as well as many other health problems,” the researchers write. And that can big a big money saver: A 2012 study found that the average total expenditures per adult for the treatment of heart disease were $4,279.

Also see: A night owl gene keeps some people up late at night

Of course, that’s easier said than done — especially when you’re dying to marathon those TV shows you missed all week. But you’ll need to do the basics, like keeping electronics out of the bedroom, avoiding caffeine later in the day and limiting alcohol consumption. You also may want to try this scientist’s savvy trick for falling asleep.

And whenever you fall asleep and wake up, the CDC recommends you aim for seven or more hours of sleep each night and making sure you get quality sleep. To do that, keep your bedroom dark and quiet and avoid large meals before bedtime, they recommend, the National Sleep Foundation says.