Can too little or too much sleep increase risk for Alzheimer's? Study supports 'sweet spot'

Sleep quality has proven to be important for good health, but how long a person sleeps is also important, especially as they get older. New research shows that sleeping too much or too little could have a negative impact on the brain.

A peer reviewed study published by the journal JAMA Neurology found that people who sleep six hours or less every night had elevated levels of beta-amyloid — a protein that accumulates to form amyloid plaques.

Amyloid plaques are one of the first markers of Alzheimer’s disease, according to Joseph Winer, a postdoctoral fellow at Stanford University and head researcher on the study.

The study also revealed that adults who sleep longer than nine hours showed increased signs in depressive symptoms, body mass index and cognitive decline. The sweet spot is sleeping anywhere from seven to eight hours, according to the study.

The study set out to investigate the associations between self-reported sleep duration on cognitive performance and healthy aging.

“This study is unique because we found that you can’t just make a blanket statement that all bad things happen to short and long sleepers,” Winer told USA TODAY. He added that this study “suggests there’s something happening in short sleeps that looks like Alzheimer’s disease” and that there is still a mystery with long sleepers.

The study had one the largest sample sizes recorded, with 4,417 men and women aged 65 to 85 included and it was conducted in 67 sites in the U.S., Canada, Australia and Japan, Winer said.

In the past, Alzheimer sleep studies were conducted with less than 100 people and people from a similar geometric area.

“The larger data size was really exciting because the more information you have, the more it feels like you’re measuring something real,” Winer added.

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The new research didn’t come without its limitations, however. It relied on participants self-reporting how much sleep they got. Participants also didn’t give information regarding health issues such as cardiovascular disease or diabetes, which could explain some of the differences.

There are more than 6 million Americans living with Alzheimer's, according to the Alzheimer's Association. It kills more people than breast cancer and prostate cancer combined and deaths have increased 16% during the COVID-19 pandemic.

Winer says while there isn’t enough evidence to show if getting better sleep while younger would decrease chances of getting Alzeihmer's, “it is important to maintain health sleep, especially as you get older.”