The Guardian: Brendan Lucey, MD, associate professor of neurology and director of the Washington University Sleep Medicine Center, speaks about his new study.

There’s an association between less than five and a half hours’ sleep and, more surprisingly, more than seven and a half hours’ sleep and reduced cognitive performance for older adults.

So how much is right for the over-75s? The “sweet spot” is somewhere in the middle range, between five and a half and seven and a half hours’ kip.

What else is associated with cognitive decline in older people? Alzheimer’s is the main cause, contributing to around 70% of dementia cases. “It’s been challenging to determine how sleep and different stages of Alzheimer’s disease are related,” said Lucey. “But that’s what you need to know to start designing interventions.”

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