tldr:

In a study published in the journal Nature, scientists narrowed down a “sweet spot” of between 6.4 and 7.8 hours of sleep per night. Sleep durations that fall too much on either side of that, the study found, were associated with accelerated aging.

“I would treat this as guidance,” Wen told WaPo. “The key point is consistent sleep time, around 6 to 8 hours per day. We know that’s going to do good for your overall health.”