The way we sleep can have a lasting impact on our brain health as we age. A new study from the University of Arizona has found that some common sleep behaviors may be linked to signs of aging in the brain.
Research published in journals Alzheimer’s disease and dementiaused existing brain scans and survey responses from more than 23,000 middle-aged and older adults in a large biomedical database. This study is part of a broader collaborative project between the University’s Department of Psychology, the Zuckerman School of Public Health, and the University of Southern California.
The researchers identified three sleep behaviors that were clearly associated with markers of brain aging in healthy people: sleeping outside the recommended seven to nine hours, frequent daytime naps, and insomnia. All three are associated with an increase in white matter lesions, areas of brain damage that can accumulate with age, and are associated with an increased risk of dementia, including Alzheimer’s disease.
Madeline Alley, the study’s lead author and a graduate research fellow in the Department of Psychology, said sleep is often studied as one global measure rather than as a collection of individual patterns or habits, which can obscure how sleep relates to brain aging.
“Sleep is a universal but complex behavior, and we still have much to learn about how different aspects of sleep relate to brain health,” Alley said.
In the study, participants completed a baseline questionnaire from 2006 to 2010 on five sleep behaviors: sleep duration, daytime napping, insomnia, unintentional daytime dozing, and snoring. About nine years later, the same participants underwent brain MRI scans, which researchers used to measure the volume of white matter lesions. The study was conducted in collaboration with lead co-investigator David Reichlen, professor of human and evolutionary biology at the University of Southern California.
All five behaviors were initially associated with larger lesion volumes. But when the researchers took into account related vascular health and lifestyle factors that can also affect the brain, such as high blood pressure, smoking, and lack of exercise, three behaviors continued to stand out: sleeping outside recommended ranges, frequent daytime naps, and increased insomnia. No snoring or unintentional daytime dozing occurred.
The findings regarding daytime naps were particularly interesting because research has shown that short naps may also benefit alertness and cognition. Gene Alexander, the study’s lead author and professor in the psychology department, said the survey did not capture details about the length or timing of individual naps. Future studies should test whether short, occasional naps have different effects on the brain over time than long, frequent naps.
In a follow-up analysis, the researchers looked more closely at their sleep duration and found that participants who slept less than seven hours a night had increased lesion volume compared to those who slept within the recommended range.
“Our findings suggest that getting too little sleep may increase the amount of white matter lesions in the brain as we age,” Alexander said. “While we did not see a significant effect on white matter in those who reported longer sleep times, this needs to be followed up in cohorts with longer sleepers.”
Nevertheless, Alexander said the three behaviors have common characteristics that make them particularly important to study, and each can be modified.
“Sleep is one potentially modifiable risk factor. Improving sleep quality may reduce the effects of aging on the brain, and may even reduce the risk of dementia such as Alzheimer’s disease,” Alexander said.
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