A new report by JAMA Neurology found that people who sleep six hours or less each night had elevated levels of beta-amyloid: a protein found in the brain that's considered a marker for Alzheimer's.
However, adults who slept longer than nine hours showed similar reductions to cognitive ability.
Researchers say the sweet spot for sleep is seven to eight hours per night.
According to the Alzheimer's Association, more than six million Americans are currently living with Alzheimer's disease. The association predicts this number will increase to nearly 50 million Americans by the year 2050.