Sleep fragmentation in early midlife linked with worse cognition in later years

Key takeaways:

• Researchers analyzed sleep duration and quality among 526 adults in the CARDIA study.
• Participants in the highest tertile of sleep fragmentation had more than twice the odds of having poor cognitive performance.

Sleep fragmentation, rather than sleep duration or self-reported sleep quality, in early midlife was associated with worse executive function, fluency and cognition more than a decade later, according to research in Neurology.

"The association between sleep and cognition in midlife is unclear," Yue Leng, PhD, associate professor of psychiatry at UCSF Weill Institute for Neurosciences, told Healio in an email. "The study helps to address this question and thus helps to clarify the role of sleep problems as a prodromal or risk factor for dementia." 

Researchers sought to examine associations between sleep duration and quality among a cohort of individuals in their mid-30s to late-40s, who were reassessed for cognition more than a decade later.

They included 526 participants (58% women; 44% Black; mean age, 40.1 years at baseline) from the ongoing Coronary Artery Risk Development in Young Adults study, who had a mean sleep duration of 6.1 hours and mean sleep fragmentation index of 19.2.

Researchers assessed sleep duration and quality via a wrist device worn by all participants for 3 consecutive days on two occasions roughly 1 year apart, as well as by Pittsburgh Sleep Quality Index (PSQI), during the 2003 to 2005 evaluations. At the 2015 to 2016 follow-up interval, midlife cognition was assessed through a battery of subjective testing, which included the Digit Symbol Substitution Test (DSST), Stroop test, Rey Auditory Verbal Learning Test, Montreal Cognitive Assessment (MoCA) and the Letter Fluency and Category Fluency tests.

Multivariable logistic regression was employed to examine associations between sleep parameters and poor cognitive performance, defined as a score that was greater than one standard deviation below the mean, with adjustments made for a range of physiological, psychological and demographic parameters.

According to results, 239 study participants (45.6%) reported poor sleep, defined by a PSQI global score of greater than 5. After adjusting for demographics, education, smoking, BMI, depression, physical activity, hypertension and diabetes, researchers reported that those in the highest vs. lowest tertile of sleep fragmentation index had more than double the odds of having poor cognitive performance on the DSST (OR = 2.97; 95% CI, 1.34-6.56), fluency (OR = 2.42; 95% CI, 1.17-5.02) and MoCA tests (OR = 2.29; 95% CI, 1.06-4.94).

The link between sleep fragmentation and cognitive performance was not affected by race or sex, and objective sleep duration or subjective sleep quality was not associated with midlife cognition, results showed. 

"It helps to inform the early detection and early intervention of dementia," Leng told Healio. "Clinicians should pay more attention to patients' sleep patterns for optimal brain health."