inc.com Getting 7 to 8 Hours of Sleep May Not Be Enough for Better Brain Health. A New Study Points to 4 Other Sleep Traits Lucia Auerbach 4–5 minutes
A new study from the Karolinska Institutet in Stockholm found that people with type 2 diabetes, heart disease, or stroke who slept well had better cognitive function and greater brain volume than those with the same conditions who slept poorly.
The findings, published in the peer-reviewed Journal of the American Heart Association, suggest that sleep can be a modifiable factor in supporting brain health in people with cardiometabolic diseases. According to a 2022 study from the Friedman School of Nutrition Science and Policy at Tufts University, 93.2 percent of adults in the U.S. experience some degree of metabolic dysfunction or have at least one cardiometabolic risk factor.
The Stockholm study looked at more than 400,000 middle-aged and older adults enrolled in the U.K. Biobank, a large-scale biomedical database. Participants answered questions about five aspects of their sleep. Researchers considered participants good sleepers if they slept seven to eight hours a night, identified themselves as a morning people, didn’t snore, didn’t have insomnia, and didn’t often feel sleepy during the day. Healthy sleep may help protect the brain
Among participants with cardiometabolic disease, those who slept well performed slightly better on tests of general cognition, problem-solving, and processing speed than those who slept poorly. They also had significantly greater total brain volume, as well as more gray and white matter. Notably, the connection between sleep and brain structure was stronger in people with type 2 diabetes, heart disease, or stroke than in those without the conditions.
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Abigail Dove, a researcher at the Aging Research Center in Karolinska Institutet’s Department of Neurobiology, Care Sciences, and Society and a co-author of the study, told Inc. that there is a very strong body of evidence linking diabetes, heart disease, and stroke to poorer brain health. She said the evidence linking healthy sleep to better brain health is still emerging.
“This study is among the first to examine these factors together and ask the question, ‘Can sleep mitigate the adverse impact of cardiometabolic diseases on the brain?’” Dove told Inc., adding that her team “found robust associations between sleep and better brain MRI and cognitive outcomes among people with CMDs [cardiometabolic diseases] and healthy sleep compared to those with CMDs and poor sleep.”
Because sleep is a complex and multidimensional behavior, Dove said, that the researchers had to use a composite score that combined all five sleep characteristics, which can often interact with one another.
“Someone with frequent insomnia may also feel more daytime sleepiness, and having a late chronotype may lead to shorter sleep duration,” Dove said.
Because the researchers did not analyze the five characteristics separately, Dove said that she cannot say which mattered most in this study. A 2025 study by Dove and her colleagues found that sleep duration and chronotype were the characteristics most strongly related to brain health.
Importantly, Dove told Inc. that this is just one study and that the results must be replicated using other data sets, “specifically ones that are more racially and socioeconomically diverse than the U.K. Biobank.” The study is also observational, meaning it cannot show that healthy sleep causes better brain health. Participants also self-reported their sleep rather than having it measured directly.
Still, Dove said the main takeaway is that healthy sleep may mitigate the the poorer cognition and brain health linked to cardiometabolic diseases.
“I think this is a very positive and empowering message since improving sleep is an achievable goal for most people,” Dove said.
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