People with Type 2 diabetes, heart disease, or stroke who slept well had better cognitive function and larger brain volume than people with the same conditions who slept poorly, according to a study published Nov. 4 in the Journal of the American Heart Association [1][2].
The results suggest that healthy sleep may support cognitive and brain health in people with cardiometabolic diseases (CMD), the study authors wrote [3].
Study Methods and Cognitive Findings
According to MedicalNewsToday, the researchers looked at more than 400,000 people with CMD and those without [3]. The authors found that those with CMD who slept better had improved performance in areas like cognitive functioning and processing speed. Moreover, CMD patients with better sleep quality also had a larger total brain volume.
The outlet noted that the study was observational – thus, it cannot confirm a direct link between the quality of sleep and brain function. Nevertheless, the findings suggest that getting better sleep may help address the negative effects of CMDs on the brain.
Dr. Alex Dimitriu, founder and Menlo Park Psychiatry and Sleep Medicine in California, commented on the study's findings. According to Dimitriu, who wasn't involved in the study, the paper "reinforces the understanding that sleep is one of the most significant contributors to cognition and brain health." He added: "Good sleep was found to be a major protective factor in people with CMD, preserving processing speed, and, equally impressively, brain volume.”
Potential Mechanisms: Inflammation and Glymphatic System
The study authors suggested that the improved cognitive function among CMD patients who slept well stems from reduced inflammation and improved function of the glymphatic system. They explained that sleep supports brain health through the glymphatic system. This system, located in the central nervous system, clears metabolic waste such as amyloid-beta plaques commonly linked to Alzheimer's disease [3].
Cardiologist Dr. Amit Blumfield, who wasn't involved in the study, remarked: "Poor sleep is also related to higher rates of metabolic disease, diabetes, hypertension and inflammation – all of which are associated with earlier cognitive decline and increased rates of dementia."
Dimitriu also explained that sleep "modulates the immune system and can reduce inflammation, which is not good in any part of the body, and especially in the brain, where it can lead to impaired healing, reduced cognition, and mood symptoms like depression." Other research has tied sleep quality to broader health outcomes.
Dimitriu compared glymphatic system to "a power wash for the brain, which only happens at night." He added that the system "clears numerous toxins and metabolic products" from the brain [3].
Expert Guidance on Improving Sleep Quality With CMD
Cardiologist and lipidologist Dr. Yu-Ming Ni, who wasn't involved in the study, shared some tips on how CMD patients can improve the quality of sleep they get at night [3]. According to him, good sleep starts with creating an environment that promotes it.
"If outside light enters your bedroom, blackout curtains or an eye mask are reasonable options. You can also dim the lights in the evening, turn off unnecessary lights and limit bright screens before bed," Ni explained [3]. "The goal isn't to create perfect darkness at all costs, but to minimize unnecessary light and make your sleep environment as comfortable and conducive to sleep as possible."
Abigail Dove, the study's corresponding author and a researcher at the Karolinska Institutet in Sweden, told MedicalXpress: "Cardiometabolic diseases are very common in older adults, and they are among the most well-established risk factors for declining cognitive and brain health" [2].
"Our findings suggest that healthy sleep may help offset some of the adverse consequences of cardiometabolic disease for the brain," Dove added. "This is meaningful because for most people, improving sleep is an accessible and achievable goal" [2].
References
- Healthy Sleep Mitigates the Association Between Cardiometabolic Disease. https://www.ahajournals.org/doi/full/10.1161/JAHA.126.051940
- Good sleep linked to better brain health in cardiometabolic disease. https://medicalxpress.com/news/2026-11-good-linked-brain-health-cardiometabolic.html
- Quality sleep supports brain health in stroke, diabetes, heart disease. https://www.medicalnewstoday.com/articles/quality-sleep-supports-brain-health-stroke-diabetes-heart-disease
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