Adults in their 60s and 70s who sleep for more than eight or nine hours a night may double their chances of developing dementia, according to a recent study.
Experts at the University Hospital of Madrid and Columbia University in N.Y. sought to examine the association between sleep duration and dementia in a population at highest risk for the condition. A total of 2,700 men and women, aged 60 to 70, were the representative sample size for the three-year study.
At the beginning of the study, the participants were assessed using the mini-mental state examination (MMSE), a test designed to assess changes in brain function, according to the Daily Mail. MMSE is made up questions and tests to evaluate an individual's different mental abilities, such as memory, attention, and language. This exam is most commonly used to help doctors diagnose dementia and to assess its progression and severity, according to the Alzheimer’s Society.
To evaluate sleeping patterns, the researchers told the patients to keep a detailed record of their bedtime habits, including how many hours they slept on average in a 24-hour period. Forty-nine percent of the participants were classified as “normal” sleepers getting approximately six to eight hours a night, 40 percent were long sleepers who got more than nine hours a night, and the remaining 11 percent averaged five or less hours of sleep, Headlines & Global News reports.
The participants were then asked to take the MMSE test again at the end of the three-year study. All three groups received lower scores than they had three years earlier. While cognitive decline was present throughout all groups, a significantly rapid decline was seen in the group of long sleepers. Those that received more than nine hours of sleep a night experienced memory loss almost twice as quickly as normal sleepers did.
"Since sleep duration is potentially modifiable, the relation between sleep duration and cognitive decline might well have practical implications for the primary prevention of [dementia and cognitive] disorders,” wrote the Spanish research team.
Doug Brown of the Alzheimer’s Society supports the recent findings and suggests that sleeping patterns do impact a person’s mental health. "This research suggests that the length of time you sleep and cognitive health might be linked,” Brown said, reports the Daily Mail. "But further studies are needed to understand whether sleep duration is a cause or effect of cognitive decline."
Too much sleep, or sleeping for more than nine hours, has long been speculated to be associated with the increase of numerous diseases in individuals who are initially healthy. A study cited by the Division of Sleep Medicine at Harvard Medical School suggests that sleeping too little (less than six hours) or too much (more than nine hours) increased the risk of coronary heart disease in women.