Relationships between sleep stages and changes in cognitive function in older men: the MrOS Sleep Study

Study objective To investigate the associations between sleep stage distributions and subsequent decline in cognitive function in older men over time. Design A population-based prospective substudy of the Osteoporotic Fractures in Men Study. Settings Six sites in the United States. Participants Community-dwelling men aged 67 y or older (n = 2,601), who were free of probable dementia at sleep visit. Follow-up averaged 3.4 y. Measurement and results Sleep stages were identified by in-home polysomnography at the initial sleep visit (2003-2005). Cognitive outcomes were assessed with the Trail Making Test Part B and Modified Mini-Mental State Examination (3MS) at sleep visit and two follow-up visits. After adjusting for multiple confounders compared with men in the lowest quartile of percent of sleep time spent in Stage N1, those in the highest quartile had a twofold increase in cognitive decline for both cognitive tests (adjusted annualized percent change/y: Trail Making Test Part B Q1 = 1.06, Q4 = 2.45, P = 0.01; 3MS Q1 = -0.27, Q4 = -0.48, P = 0.03). In addition, compared with men in the highest quartile, men in the lowest quartile of percent of sleep time in Stage R revealed more cognitive decline on the 3MS (adjusted annualized percent change/y: Q1 = -0.49, Q4 = -0.22, P = 0.003). These findings were consistent even after further adjustment of total sleep time and sleep disordered breathing. No significant relationships between other sleep stages (N2, N3) and cognitive change were found. Conclusion Increased time in Stage N1 and less time in Stage R are associated with worsening cognitive performance in older men over time.