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Sleeping Too Little And Too Much Leads To Cognitive Decline

According to this new JAMA study

You know it – a lack of sleep takes a toll on your body, depressing various functions including reducing our cognitive and memory powers to a similar degree as alcohol intoxication.


But a new JAMA study says both sleeping too little (four hours or less) and too much (10 hours or more) could spell cognitive decline. The magic number for optimal cognitive performance, according to the research? Seven hours.


Cohorts of 28,756 people – all over age 45 – living in China and the U.K. reported their nightly sleep duration and underwent cognitive assessments to examine memory, executive function and orientation. The process was repeated four years later.


Researchers found a U-shaped association between sleep duration and cognitive function. They also observed that cognitive function declined faster in people with either very short or very long sleep durations than people who slept seven hours a night. Findings were consistent in both English and Chinese cohorts, despite ethnic and cultural differences between the participants.


Whilst there are other potential contributing factors such as BMI, chronic diseases and education that are associated with cognitive decline (and which researchers did control for in the study) the takeaway here is: Catch your Z’s, 7 hours for good measure.