Sleeping less than 7 hours or more than 9 hours, frequent daytime naps and insomnia are linked to greater volume of white matter lesions, areas of damage in the brain that can accumulate with age and are tied to a higher risk of dementia, including Alzheimer’s disease

> The study, published in the journal Alzheimer’s & Dementia, used existing brain scans and questionnaire responses from more than 23,000 middle-aged and older adults from a large biomedical database

>For the study, participants completed a baseline questionnaire from 2006 to 2010 on five sleep behaviors: sleep duration, daytime napping, sleeplessness, unintentional daytime dozing and snoring. About nine years later, the same participants underwent brain MRI scans, which the researchers used to measure white matter lesion volumes. The study was conducted in collaboration with David Raichlen, the lead collaborator at the University of Southern California, and a professor of human and evolutionary biology. 
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>All five behaviors were initially associated with greater lesion volume. But after the researchers accounted for related blood vessel health and lifestyle factors that can also affect the brain, such as high blood pressure, smoking and physical inactivity, three behaviors continued to stand out: sleeping outside the recommended range, frequent daytime napping and greater sleeplessness. Snoring and unintentional daytime dozing did not.
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>The findings on daytime napping were particularly interesting, since research shows short naps may also be helpful for alertness and cognition. Gene Alexander, the study’s senior author and a professor in the Department of Psychology, said that the questionnaire did not capture details on the length or timing of individual naps. Future work will need to test whether shorter, occasional naps have different effects on the brain over time compared to longer, more frequent ones.
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>In a follow-up analysis, the researchers took a closer look at sleep duration and found that participants sleeping fewer than seven hours per night had increased lesion volume compared to those sleeping within the recommended range.

[Associations of sleep behaviors with white matter hyperintensity volume in middle‐aged to older adults – Ally – 2026 – Alzheimer’s & Dementia – Wiley Online Library](https://alz-journals.onlinelibrary.wiley.com/doi/10.1002/alz.71457)

I would expect napping would clean up your brain more, but it seems maybe this is only during rem sleep

So….anything but 7 or 8 hours of sleep is bad.  That’s just fantastic.  

Sleeping less creating problems seems intuitive, but are we sure that we did not mix up cause and effect? Ie.: greater volume of white matter lesion or whatever thats causing the lesion makes your sleep abnormal

Is this chronic or episodic? Like, if average sleep is within the 7-9, you’re good? Because I often do a 5 one night and 9 the next.