Sleeping more than nine hours per night is associated with smaller brain and gray matter volume in older Hispanic adults, according to a study led by researchers at the University of Miami Miller School of Medicine.

The study was published in Alzheimer’s & Dementia.

“This study reinforces the importance of sleep duration on brain aging, as well as cognitive impairments and physical health,” says Alberto Ramos, MD, MS, professor of clinical neurology and research director, Sleep Disorders Program, and principal investigator of the nationwide Sleep in Neurocognitive Aging and Alzheimer’s Research initiative, in a release. “Sleep studies are particularly important for Hispanics, who have up to four times the risk for Alzheimer’s disease and related dementias, compared with non-Hispanic whites.”

Researchers recruited 2,334 Hispanic participants, ages 35 to 85, to undergo neuroimaging and subsequently self-report sleep duration. Using MRI, the researchers found that increased sleep was associated with smaller brain volume and smaller regions of gray and occipital matter, especially in those 50 and older.

“One possible explanation for these findings is that long sleep duration is a marker for underlying cardiovascular or psychological conditions,” says Ramos, a member of the National Institutes of Health Sleep Disorders Research Advisory Board, in a release.

Ramos notes that the new study complements his previous research showing that long sleep duration predicts cognitive decline, pointing to both functional (cognitive) and structural (volume) brain changes in this at-risk group.

“Our sleep disorder studies have significant clinical implications,” he says in the release, adding that individuals who sleep for more than nine hours or have other issues, like insomnia, should talk with a primary care physician or see a specialist. “Don’t ignore a poor sleep pattern. It could be an indicator of an underlying medical problem that should be addressed now, rather than later.”

Funded by the National Institute on Aging and National Heart Lung Blood Institute, the collaborative study included researchers from Wayne State University, San Diego State University, Harvard Medical School, Albert Einstein College of Medicine, University of North Carolina, University of Illinois, University of California, San Diego, and University of California, Davis.

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