If you’re in the habit of trying to get eight hours of sleep a night, you might want to start setting your alarm 30 minutes earlier.
Because seven and a half hours is the ‘sweet spot’ to preserve the brain and offset Alzheimer’s disease, a study shows.
Those who get too little or too much sleep experience greater cognitive decline, according to research.
Associate professor of neurology at Washington University Sleep Medicine Centre Dr Brendan Lucey said: ‘Our study suggests that there is a middle range, or ‘sweet spot’, for total sleep time where cognitive performance was stable over time.
‘Short and long sleep times were associated with worse cognitive performance, perhaps due to insufficient sleep or poor sleep quality.’
In the study, published in the journal Brain, 100 older adults with an average age of 75, slept with a tiny monitor strapped to their foreheads most nights to measure brain activity during sleep for an average of four-and-a-half years.
cientists also took cerebrospinal fluid – found within the tissue that surrounds the brain and spinal cord – to measure levels of Alzheimer’s proteins.
Cognitive scores declined for the groups that slept for what would be the equivalent of less than five and a half or more than seven and a half hours per night.
Previous research has found that memory loss, confusion and being slower to learn new things, all symptoms of Alzheimer’s, are linked to poor sleep.