Managing disorders involving either too little or too much sleep may be a promising target for prevention of cognitive decline, researchers suggest.

They say there is a U-shaped relationship between sleep and dementia, suggesting the risk of developing cognitive disorder or Alzheimer’s disease rises significantly when nocturnal sleep duration is less than four hours or more than 10 hours.

“The optimal [nocturnal sleep] duration was found to be roughly 5.6–6 hours for lower risk of cognitive disorder and 5.6–7 hours for lower risk of AD,” the authors wrote.

“Similar results were obtained for the associations with total daily sleep duration: the protective window was situated between 5.6 and nine hours for lower risk of cognitive disorders.”