The CHARMS study: rationale and study protocol for an observational study of sleep and biobehavioral rhythms in older adult couples

Individuals with mild cognitive impairment (MCI) demonstrate cognitive decline without major functional impairment and are at increased risk for developing Alzheimer's disease and related dementias (ADRD). Sleep and biobehavioral rhythm disturbances (disruptions in 24-h 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. Importantly, the consequences of sleep and biobehavioral rhythm disruption in MCI extend beyond the patient, also profoundly affecting the spouse/partner. However, scant research has investigated sleep and biobehavioral rhythms that may contribute to the health and cognitive functioning of individuals with MCI and their partners. The current paper presents the rationale and methods for the Couples Healthy Aging and Rhythms (CHARMS) study, a longitudinal cohort study of sleep and biobehavioral rhythms among older couples in which one partner evidences cognitive decline but is independent in daily functioning. The targeted enrollment goal will consist of 185 couples who meet study eligibility criteria including that one partner shows evidence of cognitive decline but reports being independent in daily activities. This is a longitudinal observational study that includes a baseline assessment, a seven-day at-home naturalistic study protocol, and a two-year follow-up to examine change over time. Findings from this 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 ADRD.