Participação dos componentes homeostático e circadiano do sono no desempenho funcional em idosos institucionalizados

Abstract

Introduction: Aging is one of the phenomena that affect the regulation of the sleep-wake cycle (SWC) and its components, the circadian and homeostatic. Disorders in the SWC regulation are related to an important health status indicator in the elderly population, the functional performance, whose progressive decline is known to be a usual Frailty Syndrome characteristic. Both pathological entities largely affect the institutionalized elderly, who are at greater risk of developing a faster deterioration process. Aim: Evaluate the influence of two sleep components, the homeostatic and circadian, on functional performance among institutionalized elderly. Materials and methods: Longitudinal study that lasted 24 months, with three evaluation procedures, conducted with 133 elderly people living in fourteen long-term institutions in the State of Paraíba, Brazil. The Pittsburgh Sleep Quality Index (PSQI) and actimetry (nonparametric approach) were used, in addition to specific questionnaires and tests to access variables in general health and functional performance (frailty phenotype). Descriptive statistics were used for sample characterization, with distribution measures for all variables. Then, bivariate analyzes were performed in order to observe associations between the independent and dependent variables, and the Effect-Size was calculated for each variable. Lastly, linear models of mixed effects were developed and adjusted by covariates in order to analyze whether changes in sleep quality (latency, duration, beginning as well as end of sleep, and PSQI score) and rest-activity rhythm (L5, M10, IS60, ISm, IV60 and IVm) would be predictors of frailty burden increase. Results: The sample was characterized by average age of 78.76 (± 7.62) years-old, poor sleep quality, PSQI (7.71 ± 4.38 points), and 47.3% of frail elderly. The frail elderly had worse sleep quality, PSQI = 9.00 (± 4.59), when compared to non-frail, PSQI = 6.42 (± 3.74) (p = 0.001). The elderly with poor sleep quality complaints, prolonged sleep latency, inadequate sleep duration, low habitual sleep efficiency, nocturnal and daytime sleep disorders and/or use of sleeping medication displayed positive criteria for exhaustion, unintentional weight loss, decline in walking speed, grip strength and physical activity. In addition, it was observed a greater irregularity and fragmentation of the rest-activity rhythm among the frail elderly [ISm = 0.32 ± 0.14, p = 0.041) (IVm = 0.88 ± 0.23, p = 0.032), respectively]. Among the sleep quality variables, the PSQI global score was a predictor of frailty burden increase (β = 0.04, p = 0.003). And, of all rest-activity rhythm variables, only the intra-daily variability (IVm) was able to predict changes in frailty (β = 0.906; p = 0.034). Conclusion: Based on this longitudinal study results it was observed that poor sleep quality and rest-activity rhythm fragmentation were predictors of frailty burden increase among institutionalized elderly, that is, the homeostatic component was the main influencer of progressive decline in functional performance, concerning the frailty status. It should be noted that sleep-activity rhythm and sleep quality markers can be a new tool in monitoring the health and disease status in institutionalized elderly.