Individuals whose sleep is characterized by high restlessness at about 40 years of age may have a higher risk of poor cognitive functioning 11 years later compared with individuals whose sleep is better, according to a prospective cohort study published yesterday in Neurology.
“Since Alzheimer’s disease pathology begins to accumulate in the brain many years before symptom onset, it’s possible that sleep disturbances identified in late life—close to the time when memory loss becomes apparent—is actually the consequence of this pathology that has been developing silently over the years,” said Yue Leng, Ph.D., of the University of California, San Francisco, in a news release.
Leng and colleagues used data from the Coronary Artery Risk Development in Young Adults (CARDIA) study, during which participants were assessed every two to five years over 30 years. The current study took place from 2003 to 2005 and included 526 White and Black adults with a mean age of 40 years (58%/42% women/men and 66%/44% White/Black). Participants wore wrist activity monitors for three consecutive days and nights on two occasions about one year apart. The wrist monitors measured both sleep duration and each participant’s sleep fragmentation index, a measure of restlessness during their sleep calculated by measuring the amount of time they spent moving and the amount of time they were still for one minute or less. Participants also reported the times they went to bed and woke up and the quality of their sleep by completing the Pittsburgh Sleep Quality Index.
Cognitive assessments were conducted about 11 years later. Interviewers administered tests that assessed the participants’ processing speed, executive function, working memory, verbal memory, fluency, and global cognitive function.
Participants slept an average of about six hours a night, and 45.6% reported poor-quality sleep. While there was no relationship between sleep duration and cognition, participants with the greatest amount of sleep fragmentation were two to three times more likely than participants with moderate or low sleep fragmentation to have poor cognitive performance 11 years later on nearly all the cognitive measures except verbal memory. These findings did not differ by race or sex.
“This research contributes to a body of literature that underscores the need to evaluate modifiable risk factors associated with cognitive aging,” said the study’s senior author Kristine Yaffe, M.D., in the news release. “Future research is needed to study the link between sleep disturbances and cognition at different stages of life and to identify whether there are critical life periods when sleep is more strongly associated with cognition. ... This might open up new opportunities for the prevention of Alzheimer’s in late life.”
For related information, see the Journal of Neuropsychiatry and Clinical Neurosciences article “Specific Sleep Health Domains as Predictors of Executive Function in Older Adults.”
(Image: Getty Images/iStock/RealPeopleGroup)
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