“Our study suggests that there is a middle range, or ‘sweet spot,’ for total sleep time where cognitive performance was stable over time,” said researcher Dr. Brendan Lucey. “Short and long sleep times were associated with worse cognitive performance, perhaps due to insufficient sleep or poor sleep quality.”
The link between sleep and cognition
For the study, the researchers analyzed data from 100 participants involved in Washington University’s Alzheimer Disease Research Center. The participants slept with an EEG to measure brain activity for four to six months. They also provided cerebrospinal fluid and blood samples to test for markers of Alzheimer’s disease and took cognitive exams each year.
The researchers learned that two groups of participants experienced the greatest cognitive decline: those who slept fewer than 5.5 hours per night and those who slept more than 7.5 hours per night. Participants who fell somewhere in between that range showed no additional risk for significant cognitive issues.
“It was particularly interesting to see that not only those with short amounts of sleep, but also those with long amounts of sleep had more cognitive decline,” said researcher Dr. David Holtzman. “It suggests that sleep quality may be key, as opposed to simply total sleep.”
Treating sleep issues
The researchers say consumers who experience persistent sleeping issues should work with their doctors to identify potential treatments. This is especially true for consumers currently struggling with both cognitive decline and poor sleep.
“I ask many of my patients, ‘How’s your sleep?’” said researcher Dr. Beau M. Ances. “Often patients report that they’re not sleeping well. Often once their sleep issues are treated, they may have improvements in their cognition. Physicians who are seeing patients with cognitive complaints should ask them about their quality of sleep. This is a potentially modifiable factor.”