THE ARISING · Longevity & Healthspan
Good Sleep Linked to Larger Brains in People With Cardiometabolic Disease
Adults with type 2 diabetes, heart disease or stroke who had healthy sleep patterns had larger brains and scored higher on some thinking tests than adults with the same conditions who slept poorly, according to a study in the Journal of the American Heart Association.
The work is an observational analysis of 408,977 adults in the UK Biobank, a large health database. Of these, 54,017 (13.2%) had at least one cardiometabolic disease at the start. That term covers type 2 diabetes, heart disease and stroke, all of which are important risk factors for dementia. Brain MRI scans were available for a subsample of 34,913 people.
The researchers scored sleep using five measures: how long people slept, chronotype (whether they are naturally morning or evening people), insomnia symptoms, snoring and daytime sleepiness. Each person was placed in a healthy, intermediate or poor sleep group. Disease status was drawn from medical records, medication use and medical history.
Among people with a cardiometabolic disease, those with healthy sleep did better than those with poor sleep on global cognition (β=0.02, 95% CI 0.01–0.05), verbal and numeric reasoning (β=0.07, 95% CI 0.01–0.12) and processing speed (β=0.07, 95% CI 0.04–0.10). Processing speed is how quickly a person can take in and respond to information.
The brain scans showed a similar pattern. Compared with poor sleepers who had a cardiometabolic disease, healthy sleepers with one had larger total brain volume (β=0.22, 95% CI 0.08–0.35), gray matter volume (β=0.23, 95% CI 0.09–0.36) and white matter volume (β=0.19, 95% CI 0.05–0.33). Gray matter holds the brain's nerve cell bodies. White matter carries the connections between them. The authors describe smaller brain volume as a marker of brain atrophy, or shrinkage.
The authors conclude that healthy sleep may attenuate the links between cardiometabolic disease and poorer cognitive performance and brain atrophy markers. They describe sleep as a modifiable factor that may support cognitive and brain health in people with these conditions.
The next question is whether improving sleep in people with these conditions changes their brain and cognitive outcomes over time.
This was not a sleep intervention trial. The associations cannot show that improving sleep increases brain volume or prevents dementia.