Why Did Long Sleep Line Up With Earlier Death?

Seven to nine hours is the sweet spot for sleep and all-cause mortality. Below seven hours, shorter sleep predicts a shorter life. Past nine hours the mortality curve stops going down, and at ten or eleven hours it hooks back up, almost like a J shape tilted over and reversed.

Sleep science has at least two explanations, and they are not mutually exclusive. The first is that the illness which took their lives was too much for sleep to deal with. When people get sick, an inflammatory, cytokine-mediated response makes them want to sleep more and curl up in bed. They were calling on sleep, the Swiss Army knife of health, but the illness was too powerful for sleep to overcome. The pattern then looks as though more sleep leads to a higher risk of death, while sleep was responding to the mortality risk and lost the battle.