Dyadic Sleep, Biobehavioral Rhythms and Cognitive Function in Older Adults: Implications for Alzheimer’s Disease

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Abstract Individuals with mild cognitive impairment (MCI) demonstrate cognitive decline without major functional impairment but also experience a 7-fold increased risk for developing Alzheimer’s disease, a leading cause of poorer quality of life (QOL), premature mortality, and health care expenditures. Sleep and biobehavioral rhythm disturbances (disruptions in 24h oscillations in physiology and behavior, including rest-activity patterns and mealtimes) are more than twice as common among patients with MCI than cognitively intact older adults. Emerging evidence demonstrates a mechanistic role of sleep and biobehavioral rhythm disturbances in cognitive decline and the development and progression of Alzheimer’s disease. Importantly, the consequences of sleep and biobehavioral rhythm disruption in MCI extend beyond the patient, also affecting the spouse/partner, as sleep is a “shared” health behavior for most adults. However, sleep and biobehavioral rhythms are typically considered at the level of the individual. Building on our team’s pioneering work on sleep as a shared experience among couples, we propose to investigate sleep and biobehavioral rhythms as fundamental dyadic processes that contribute to the health and cognitive functioning of individuals with MCI or mild AD and their partners. We will evaluate the daily and longitudinal effects of two dyadic processes in sleep: interdependence (partners’ sleep patterns influence on each other) and concordance (i.e., the couples’ similarity in rest/activity and social rhythms such as meal timing). We will conduct a 14-day naturalistic study protocol in order to examine the mechanistic associations between sleep and biobehavioral rhythms and proximal indicators of daytime functioning, within a sample of 170 couples in which one partner evidences cognitive impairment (MCI to mild Alzheimer’s disease). During the naturalistic study protocol, we will capture sleep and biobehavioral rhythms via objective (actigraphy) measures of sleep and circadian rest-activity rhythms and daily social rhythms, respectively. Also, we will include daily assessments of mood and relationship quality, and we will use an innovative smartphone cognitive assessment that has been validated to measure cognitive function in daily life. In addition, we will conduct comprehensive neuropsychological assessments at baseline and again at two-year follow-up to examine how sleep and biobehavioral rhythm disruptions at baseline predict cognitive decline over 2 years in both partners. Results of study will advance the understanding of the daily and longitudinal relationships between the individual and couple-level processes in sleep and biobehavioral rhythms that influence the progression of cognitive decline in a population at increased risk for developing Alzheimer’s disease.