a bed near a windowMost people agree that sleep plays a critical role in brain function, but is it quality or quantity that matters most? Researchers from the California Pacific Medical Center Research Institute (CPMCRI) in San Francisco, California studied how sleep quality affected a population of older men. The results indicate that poor quality of sleep accelerates cognitive decline.

For this population-based, longitudinal study, the research team worked with 2,822 older men with an average age of 76 who were located at six clinical centers. They collected an average of five nights’ worth of sleep data from the men using a wrist actigraph, which is a device that records the user’s movement. They assessed the participants’ executive function—the ability to plan, make decisions, and think abstractly—using the Trails B test, a cognitive test that measures task switching and visual attention.

The results indicate that there is a relationship between poor sleep quality and cognitive decline, even when adjusted for factors like depressive symptoms, co-occurring disorders, or medication use. The men whose sleep was more fragmented had a 40 to 50 percent increase in the risk of clinically significant decline in executive function. The decline from poor sleep quality was commensurate with that of a five year increase in age.

This study is an important step for understanding the relationship between sleep and cognition, but there is still more research to be done. The underlying mechanisms linking sleep and cognition are not yet understood.

“It was the quality of sleep that predicted future cognitive decline in this study, not the quantity. With the rate of cognitive impairment increasing and the high prevalence of sleep problems in the elderly, it is important to determine prospective associations with sleep and cognitive decline,” stated lead author Terri Blackwell, MA, senior statistician at CPMCRI.

This research is published in the journal Sleep.

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