You may think that sleeping longer or later on the weekends is good for you. But, University of Arizona researchers say changing your sleep patterns between work and play causes something called “social jet lag.”

Michael Grandner is director of UA’s Sleep and Health Research Program.

He said getting enough sleep or catching up on sleep is not enough. The key is keeping your sleep timeline the same. His study shows that changing when you sleep, by even an hour, can produce a jetlag-like effect that leads to illness.

“You are more likely to have heart disease. Your depression scores went up. Your fatigue scores went up. Your daytime sleepiness scores went up," Grandner said. "It tends to produce unpleasant outcomes rather than pleasant outcomes."

The study finds every hour shift in a sleep schedule is associated with an 11 percent increase in the likelihood of heart disease.