A new study has found that those people who are genetically predisposed to regular daytime
Previous research has shown that sleep canincrease cognitive performance, with short naps (5-15 minutes) providing a benefit that can last from one to three hours. Aging reduces reaction time and memory and often leads to an increase in the prevalence of cognitive impairment. Given the aging of the world's population, it is important to identify modifiable risk factors associated with cognitive performance, in particular sleep habits. To that end, researchers at University College London conducted a study that looked at whether there is a causal relationship between daytime sleep and brain health.
The study involved 378,932 peopleof European descent between the ages of 40 and 69. Using the technique of Mendelian randomization, they studied DNA fragments to determine the likelihood of people habitually sleeping. Mendelian randomization is a method of using measured variations in genes of known function to study the causal effects of modifiable risk factors.
All participants underwent cognitive testsvisual memory and reaction time. The researchers also looked at MRI scans of the brains of some of the participants for structural brain changes. In addition, the subjects were asked to report their sleep habits.
Researchers compared brain health andthe cognitive functioning of people who are genetically "programmed" to sleep, with those who are not accustomed to sleeping during the day. They found that, in general, people programmed to sleep have larger total brain volume, a marker of brain health, especially in older people. Decreased brain volume, also known as atrophy, is associated with diseases such as cognitive impairment and dementia.
Average difference in total brain volume between the twogroups of people was 2.6-6.5 years of aging. But in other measures — hippocampal volume, reaction time, and visual processing — there was no difference. The hippocampus is a complex structure deep in the brain that is associated with memory and learning. Hippocampal volume, in particular, is associated with cognitive decline.
Based on these findings, the researchers stated that there is a "modest causal relationship" between habitual daytime sleep and greater total brain volume.
The study was published in the journal Sleep Health.
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Cover photo: Asnaebsa • CC BY-SA