Too Much Sleep Might Be As Bad For Your Brain As Too Little Sleep

Too Much Sleep Might Be As Bad For Your Brain As Too Little Sleep

We’ve long talked about the importance of sleep and getting enough of it, but what if you tend to sleep more than the often recommended 7-8 hours? A new study suggests that might also negatively affect your memory and thinking.

Picture: Olly/Shutterstock

The Harvard-based Nurses’ Health Study, published in the Journal of the American Geriatrics Society, asked over 15,000 women (ages 70 and up) about their sleep habits in 1986 and 2000. The researchers then tested the nurses’ cognitive functions three times over a six-year period. Those who slept very little (five or fewer hours a day) or very much (nine or more hours a day) performed significantly less well on those memory and thinking tests than those who slept seven to eight hours a day. The scariest part? The researchers estimate the under- and over-sleepers were mentally two years older than those who slept the recommended amount.

The study also suggests poorer cognitive skills if your sleep duration changes by two hours or more over time (something that often happens as you get older), rather than having no change in your sleep amount.

The Harvard Health blog reasons that too much sleep is often associated with poor sleep quality, which in turn could affect memory and thinking.

While correlation doesn’t equal causation, and the study subjects were specifically elderly females, the takeaway for us all is to try to improve sleep quality, especially as we age.

Too little sleep, and too much, affect memory [Harvard Health Blog]


  • Ages 70 and up? People who sleep longer at that age usually do so because it’s a side effect of a drug of some kind, the kinds of drugs that affect your cognitive ability.
    So I’m going to take this “study” with a few grains of salt. There are just too many unknown factors to say “more sleep is bad”.

  • Sheesh, only measuring Nurses aged over 70. Therefore the conclusions and results only apply to that age group.
    And only measuring via a Telephone questionaire, at 2 year intervals!

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