The association between sleep parameters, cognitive functioning, and markers of brain morphology: The Maastricht...

To examine the association of objective and subjective sleep parameters with cognitive functioning and markers of brain morphology.

This cross-sectional study included 3360 participants (mean age: 59.5 ± 8.5 years; 51.1% female) from The Maastricht Study. Time in bed (TIB) and sleep breaks were objectively estimated using a thigh-worn accelerometer. Subjective sleep continuity was assessed via a single-item, and excessive daytime sleepiness was evaluated using the Epworth Sleepiness Scale. Cognitive testing was administered across three domains-memory, information processing speed, and executive functioning and attention. Markers of brain morphology (e.g. hippocampal volume, gray matter (GM) volume, and white matter volume) were assessed with 3 Tesla magnetic resonance imaging. Linear and logistic regression analyses modeled the associations.

A longer TIB (h/night) was associated with worse executive functioning and attention (Blinear = -0.052, 95% CI = -0.084 to -0.019). Categorical analyses showed that a longer TIB (≥9 h/night) was associated with worse executive functioning and attention (B = -0.088, 95% CI = -0.166 to -0.010) compared to a mid-range TIB (≥7 to <9 h/night). A curvilinear association was found between TIB and lower GM volume (Bquadratic = -0.013, 95% CI = -0.025 to -0.001). Sleep breaks (≥2/night) were associated with worse overall cognition (B = -0.069, 95% CI = -0.124 to -0.013), information processing speed (B = -0.125, 95% CI = -0.212 to -0.039), and reduced GM volume (B = -0.068, 95% CI = -0.118 to -0.018). No significant associations were found for memory or other markers of brain morphology. Subjective sleep parameters showed no associations with cognitive functioning or markers of brain morphology.

Adequate and uninterrupted TIB was associated with better cognitive functioning and brain morphology. Statement of Significance With the growing prevalence of dementia, the importance of reducing dementia risk is increasingly acknowledged. Sleep has been identified as a potential risk factor for cognitive decline and dementia, yet studies using objective measures of sleep remain limited. This study explores subjective and objective sleep parameters in relation to cognitive function and brain morphology in a large cohort. The findings show that a long time in bed (TIB) is negatively associated with executive functioning and attention, alongside a curvilinear relationship between TIB and gray matter volume. Additionally, sleep breaks (≥2/night) are linked to lower brain volume and poorer cognition. Future research should investigate longitudinal associations and other sleep aspects, including regularity and sleep disorders, to further our understanding and guide dementia prevention strategies.