Trajectories of sleep duration and quality and their association with mild cognitive impairment, frailty, and all-cause mortality.

Objectives: To identify longitudinal trajectories of sleep duration and quality and estimate their association with mild cognitive impairment, frailty, and all-cause mortality.

Methods: We used data from three waves (2009, 2014, 2017) of the WHO Study on Global Aging and Adult Health in Mexico. The sample consisted of 2722 adults aged 50 and over. Sleep duration and quality were assessed by self-report. Sleep trajectories were determined by applying growth mixture models. Mixed-effects logistic (mild cognitive impairment) and ordinal logistic (frailty), and Cox proportional hazards (all-cause mortality) models were fitted.

Results: Three classes for sleep duration ("optimal-stable," "long-increasing," and "short-decreasing") and quality ("very good-increasing," "very good-decreasing," and "moderate/poor stable") were identified. Compared to the optimal-stable group, the long-increasing trajectory had greater odds for mild cognitive impairment (odds ratio=1.68, 95% CI: 1.01-2.78) and frailty (odds ratio=1.66, 95% CI: 1.13-2.46), and higher risk for all-cause mortality (hazard ratio=1.91, 95% CI: 1.14-3.19); and the short-decreasing class had a higher probability of frailty (odds ratio=1.83, 95% CI: 1.26-2.64). Regarding the sleep quality, the moderate/poor stable trajectory had higher odds of frailty (odds ratio=1.71, 95% CI: 1.18-2.47) than very good-increasing group.

Conclusions: These results have important implications for clinical practice and public health policies, given that the evaluation and treatment of sleep disorders need more attention in primary care settings. Interventions to detect and treat sleep disorders should be integrated into clinical practice to prevent or delay the appearance of alterations in older adults' physical and cognitive function. Further research on sleep quality and duration is warranted to understand their contribution to healthy aging.