The cause may be middle-aged sleep disorder

Study author Dr. “Our results suggest that sleep quality, not quantity, is most important for cognitive health in midlife,” says Yue Ling of the University of California, San Francisco. Understanding the relationship between sleep and cognition is crucial to recognizing sleep problems as a risk factor for certain diseases. These primarily include dementia and Alzheimer's.

526 people with an average age of 40 participated in the trial over an 11-year period. The researchers examined the duration and quality of participants' sleep using activity monitors temporarily placed on the participants' wrists. Test participants also recorded their sleeping and waking times in a sleep diary and filled out questionnaires about sleep quality. They also completed a series of memory and thinking tests.

The researchers examined so-called sleep fragmentation, which measures repeated short interruptions in sleep. Ten years later, of the 175 people with the most disruptive sleep disorder, 44 had poorer cognitive performance. In contrast, only 10 out of 176 people with the least sleep disturbances had poor test results.

“More research is needed to evaluate the relationship between sleep disorders and cognition at different stages of life,” Ling says. It should also be determined whether there are critical periods of life in which sleep is most closely linked to cognition. In the future, new options may be addressed to prevent dementia and Alzheimer's disease later in life.