As the first study in a series called the Sleep and Dementia Consortium, this research looked into what markers of sleep were associated with better cognition. Before conducting the study, researchers suspected that the percentage that people spent in deeper sleep stages like stage 3 and REM would be most important for brain function.

However, after crunching the numbers, they found that better “sleep consolidation” and an absence of sleep apnea were actually the metrics most associated with better cognition. These were even more important than sleep stage percentages—previously considered gold standard metrics for sleep quality.

This finding will lay the groundwork for future research untangling the nuances of how sleep impacts the aging brain. Sleep and Dementia Consortium researchers predict that, “Sleep of sufficient quality and duration may be associated with decreased risk of dementia through several mechanisms, including augmenting the glymphatic clearance of Alzheimer’s disease proteins.”

These initial findings show the importance of monitoring and treating sleep apnea, as well as working on sleep consolidation, in order to stay mentally sharp.