Sleep experts close in on the optimal night’s sleep, reports the Wall Street Journal in both a written and video WSJ Live segment.

“The lowest mortality and morbidity is with seven hours,” said Shawn Youngstedt, a professor in the College of Nursing and Health Innovation at Arizona State University Phoenix. “Eight hours or more has consistently been shown to be hazardous,” says Dr. Youngstedt, who researches the effects of oversleeping.