Common Sleep Habits Leave Lasting Marks on the Aging Brain

How you sleep may shape how your brain ages. A new study from the University of Arizona, published in Alzheimer's & Dementia, found that three specific sleep behaviors are associated with greater volumes of white matter lesions—areas of damage in the brain that accumulate with age and are tied to a higher risk of dementia, including Alzheimer's disease.

The study drew on brain scans and questionnaire responses from more than 23,000 middle-aged and older adults sourced from a large biomedical database. Participants completed a baseline questionnaire between 2006 and 2010 covering five sleep behaviors: sleep duration, daytime napping, sleeplessness, unintentional daytime dozing, and snoring. Roughly nine years later, the same participants underwent brain MRI scans to measure white matter lesion volumes. All five behaviors were initially associated with greater lesion volume, but after accounting for blood vessel health and lifestyle factors like high blood pressure, smoking, and physical inactivity, three behaviors continued to stand out: sleeping outside the recommended seven-to-nine-hour range, frequent daytime napping, and greater sleeplessness. Snoring and unintentional daytime dozing did not. 

Lead author Madeline Ally noted that sleep is often studied as a single overall measure rather than a set of distinct patterns and habits, which can obscure the relationship between sleep and brain aging. "Sleep is a universal but complex behavior, and there is still much to learn about how different aspects of sleep relate to brain health," Ally said.

A follow-up analysis on sleep duration found that participants sleeping fewer than seven hours per night had increased lesion volume compared to those sleeping within the recommended range. Senior author Gene Alexander said shorter sleep appeared more consequential: "Our findings suggest that having too little sleep may lead to greater white matter lesion volumes in the brain as we age. We didn't see greater white matter impacts in people who reported longer sleep durations, but this needs to be followed up in cohorts with more long sleepers.

The daytime napping findings also warrant further study, since short naps have been shown to support alertness and cognition. The questionnaire did not capture nap length or timing, so future research will need to examine whether shorter, occasional naps affect the brain differently than longer, more frequent ones.

Alexander emphasized that all three behaviors share an important quality: they can potentially be changed. "Sleep is one of those potentially modifiable risk factors. If we can improve the quality of our sleep, it may help reduce the impacts of brain aging and maybe even lower the risk for dementias like Alzheimer's disease," he said.