A study has found that people who get nine hours of sleep or more every night have a much higher risk of developing dementia.
The research found that those who slept excessively also had smaller brain volumes.
Published in the journal,
Neurology, scientists at Boston University School of Medicine found that sleeping longer may actually be an early warning sign, rather than a cause of some of the patterns in the brain associated with dementia.
Sleeping so long regularly could point to problems with thinking and memory.
Participants in the study were asked to indicate how long they typically slept each night - after ten years they were examined for some of the more typical brain patterns that can indicate dementia due to Alzheimer's disease.
Co-author of the study is the professor of neurology, Sudha Seshadri:
"Participants without a high school degree who sleep for more than nine hours each night had six times the risk of developing dementia in 10 years as compared to participants who slept for less. These results suggest that being highly educated may protect against dementia in the presence of long sleep duration."
They now believed the findings will be a useful clinical tool to help predict those at risk of progressing to clinical dementia within 10 years.
