Sleep Rhythmicity as a Core Domain of Multidimensional Sleep Health Associated with Cognitive Impairment in Older Men

Sleep encompasses multiple dimensions, each potentially involving distinct parameters that collectively capture the complex features of sleep health. However, limited studies focused on the construction of objective sleep multidimensions and its associations with cognitive impairment.

The study included 2670 community-dwelling older men from the Osteoporotic Fractures in Men study. Wrist actigraphy was used to collect sleep data. Latent sleep dimensions were identified from objectively measured sleep parameters using exploratory factor analysis without prespecified structures. Longitudinal associations between sleep domains and cognitive impairment were evaluated using Cox proportional hazards models over a mean follow-up of 7.4 years. XGBoost with SHapley Additive exPlanations (SHAP) was used to rank the predictive importance of each domain.

Five dimensions of sleep health framework were identified: rhythmicity, quality, duration, regularity, and timing. Disrupted rhythmicity was significantly associated with an increased risk of cognitive impairment (HR = 1.21, 95% CI: 1.07-1.37, p = 0.002). Longer duration (HR = 1.13, 95% CI: 1.00-1.28, p = 0.043), poorer regularity (HR = 1.13, 95% CI: 1.00-1.27, p = 0.046) and lower quality (HR = 1.13, 95% CI: 1.01-1.27, p = 0.040) were also linked to elevated risk in fully adjusted model. No significant association was observed between timing and cognitive impairment. SHAP analysis indicated that rhythmicity ranked high in predictive importance compared with traditional risk factors and was the most influential domain among the sleep dimensions. After stratification, disrupted rhythmicity remained significantly associated with cognitive impairment in most demographic and lifestyle subgroups.

Our integrative modelling approach provides novel insights into the complex relationships between distinct sleep domains and cognitive impairment, highlighting rhythmicity as a key factor for preserving cognitive health in aging men. These findings suggest that sleep-related interventions, especially for management of rhythmicity, may be a promising approach for the prevention of cognitive impairment.