Association of Sleep Variables With Cognitive Performance and the Risk of Dementia in the Sleep and Dementia Consortium.

BACKGROUND AND

OBJECTIVES

Sleep is multidimensional, and it remains unclear which aspects are most relevant to cognition and dementia risk. We aimed to apply a data-driven approach to identify clusters of sleep variables that reflect meaningful sleep composites and examined their association with cognition and dementia risk.

METHODS

This was a prospective observational cohort study that used data from the Sleep and Dementia Consortium, comprising 5 US population-based cohorts. Participants aged ≥45 and ≥60 years were included in the cognitive and dementia analyses, respectively. All were free of dementia and stroke at baseline. Participants had methodologically consistent, home-based polysomnography, self-report habitual sleep, neuropsychological assessments, and dementia risk surveillance. A cluster around latent variables analysis was used to derive 9 latent sleep composites from 44 sleep metrics. Global cognitive composite z scores were derived from principal component analysis. Linear regression models assessed associations between sleep composites and cognitive performance. Cox proportional hazard models assessed associations between sleep composites and incident dementia. Results were considered statistically significant if p < 0.05.

RESULTS

The pooled cognitive analysis included 5,958 participants (mean ± SD age 70 ± 11 years, 32% female). The incident dementia analysis included 5,471 participants (74 ± 12 years, 31% female). There were 1,134 incident dementia cases (median follow-up time of 5-19 years). Nine sleep composites were identified, together explaining 49% of the total variance in the original 44 sleep metrics: Sleep quantity and efficiency, sleep fragmentation, light non-rapid eye movement (NREM) predominance, N3 predominance, spindle number and duration, REM sleep bouts, respiratory disturbances, slow oscillation-spindle coupling, and spindle amplitude. Of these, composites reflecting greater sleep quantity and efficiency (i.e., longer and more consolidated sleep; pooled β per one-unit change in composite, 0.03; 95% CI 0.004-0.06; p = 0.033) and stronger slow oscillation-spindle coupling (pooled β, 0.04; 95% CI 0.003-0.07; p = 0.039) were associated with better global cognition. However, no significant associations were identified between the 9 sleep composites and dementia risk.

DISCUSSION: Sleep composites were not significantly associated with dementia risk. However, longer, more consolidated sleep and stronger slow oscillation-spindle coupling were associated with cognitive performance. These composites may be useful in guiding further investigations of sleep-brain health relationships.