Scientists have linked sleep quality and brain health in chronic diseases

It is especially important for people with chronic diseases of the cardiovascular and metabolic systems to monitor the state of the brain: such disorders are associated with an increased risk of cognitive decline and dementia. One of the factors that may be associated with the preservation of mental abilities remains the quality of sleep. Researchers have found that people with type 2 diabetes, heart disease, or stroke have a good night's sleep combined with higher cognitive test scores and a larger brain volume. About the role that night rest can play for the health of the nervous system - in the material of Izvestia.

Sleep and brain condition

Scientists from the Karolinska Institute in Sweden studied the data of 408,977 adult participants. 54,017 people, or 13.2% of the sample, had at least one cardiometabolic disease: type 2 diabetes, heart disease, or stroke. The results of the study are published in the Journal of the American Heart Association (JAHA).

The researchers tested whether sleep patterns are related to cognitive abilities and brain structure in people with such diagnoses. The quality of rest was assessed according to five criteria: sleep duration, chronotype — preferred time of activity and rest, symptoms of insomnia, snoring and daytime sleepiness. The participants provided information about these features independently.

To assess the structure of the brain, scientists used the results of magnetic resonance imaging (MRI). Such images were available to 34,913 participants. This made it possible to compare sleep characteristics not only with the test results, but also with the volume of various brain tissues.

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The best results of cognitive tests

Participants with cardiometabolic diseases who had a healthier sleep pattern had slightly higher test results than people with the same diagnoses but poor sleep. The differences were found when assessing general cognitive abilities, problem-solving skills, and information processing speed.

In particular, more favorable indicators were associated with better results in verbal and numerical thinking tasks. However, researchers do not claim that prolonged or high-quality sleep alone improves intelligence. The work shows that the characteristics of rest and cognitive outcomes occur together, but does not establish the cause of this dependence.

The authors also noted that the association between sleep and brain health was more pronounced in people with type 2 diabetes, heart disease, or stroke than in participants without these diagnoses.

Differences in brain volume

The MRI results showed that people with cardiometabolic diseases and healthier sleep had a larger total brain volume than participants with the same diseases and poor sleep. Differences were also revealed when assessing the volume of gray and white matter.

Gray matter contains the bodies of nerve cells and is involved in information processing, while white matter provides communication between different areas of the brain. Therefore, changes in their volume may be one of the indicators of the state of the nervous system. However, by themselves, these measurements do not allow us to determine how well a person copes with everyday tasks or whether he has a cognitive disorder.

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What remains to be seen

The study does not prove that it is good sleep that leads to an increase in brain volume or an improvement in cognitive performance. The scientists compared the already existing features of rest and the health status of the participants, rather than observing the changes after a specially organized improvement in sleep.

In addition, information about the duration and quality of rest was based on the responses of the participants themselves. Other factors could have influenced the results, such as general health or lifestyle. Therefore, it cannot be ruled out that people with more favorable brain indicators generally slept better for reasons not directly related to the influence of sleep.

The authors believe that further research will help clarify which characteristics of night rest are most closely related to the preservation of cognitive functions in people with cardiometabolic diseases. So far, the results suggest that sleep is a potentially important factor in brain health, but not a proven way to prevent dementia or reverse changes that have already occurred.