Sleeping too much increases the risk of dementia. Sleeping for 9 hours will reduce memory
Researchers at the Miller School of medicine at the University of Miami studied more than 5000 Hispanic Americans aged 45 to 75 over seven years. After seven years, those who slept an average of nine hours a night lost 22% of their learning ability, 20% of their speaking fluency and 13% of their memory.
Researchers say that too much sleep is associated with a lesion in the brain called high white matter signal, leading to a decline in cognitive ability and an increased risk of dementia and stroke.