Association of Sleep Disturbances With Prevalent and Incident Motoric Cognitive Risk Syndrome in Community-Residing Older Adults.

Background and objectives: There is growing evidence that sleep disturbances are associated with cognitive impairment risk, but their association with the incidence of motoric cognitive risk syndrome (MCR)-a predementia syndrome characterized by slow gait speed and cognitive complaints-is unknown. We aimed to examine the association of sleep disturbances, overall and specific subtypes, with (1) incident and (2) prevalent MCR in older adults.

Methods: Community-residing adults aged 65 years and older without dementia were recruited from population lists and included in Central Control of Mobility and Aging, a prospective cohort study, in Albert Einstein College of Medicine, Bronx, NY. We included participants with available data for MCR and Pittsburgh Sleep Quality Index (PSQI). MCR was defined as cognitive complaints reported on standardized questionnaires and slow gait speed as recorded on an electronic treadmill and was adjudicated at baseline and annual follow-up visits. Participants were divided into "good" sleepers (≤5) and "poor" sleepers (>5) based on an established PSQI cut score. Among participants without MCR at baseline, Cox proportional hazard models adjusted for (1) age, sex, and education and (2) further for comorbidity index, Geriatric Depression Scale score, and global cognitive score were used to examine the association of baseline sleep disturbances with MCR incidence. Association between poor sleep quality and prevalent MCR at baseline in the overall population was explored using multivariate logistic regression analysis.

Results: 445 participants were included (56.9% women, mean age: 75.9 years [75.3; 76.5]). In MCR-free participants at baseline (n = 403), 36 developed incident MCR over a mean follow-up of 2.9 years. Poor sleepers had a higher risk of incident MCR (HR = 2.7 [1.2; 5.2]) compared with good sleepers, but this association was not significant after adjustment for depressive symptoms (adjusted hazard ratio [aHR] = 1.6 [0.7-3.4]). Among the 7 PSQI components, only sleep-related daytime dysfunction (excessive sleepiness and lower enthusiasm) showed a significant risk of MCR in fully adjusted models (aHR = 3.3 [1.5-7.4]). Prevalent MCR was not associated with poor sleep quality (OR [95% CI] = 1.1 [0.5-2.3]).

Discussion: Overall poor sleep quality was associated with incident MCR, but not with prevalent MCR. Specifically, older adults with sleep-related daytime dysfunction are at increased risk of developing MCR. Further studies are needed to validate mechanisms of this relationship.