Interaction between cognition, motor function, and functional disability in older adults with Alzheimer's disease

Abstract

Background: Alzheimer’s disease (AD) is characterized by progressive cognitive decline that compromises functionality and social participation. Although cognitive impairment is considered the main determinant of functional disability, motor alterations may also contribute to this process. However, how cognition and motor function relate to different domains of functional disability in this population remains poorly understood. Objective: To investigate the interaction between cognition, motor function, and functional disability in people with AD, and to evaluate how cognitive and motor performance are associated with disability. Methods: A cross-sectional observational study, conducted according to the STROBE guidelines, and included 27 participants of both sexes with a mean age of 72.19 years, assessed in a single session by trained physiotherapists. Depressive symptoms were assessed using the Geriatric Depression Scale (GDS); balance responses using the Balance Evaluation Systems Test (BESTest); motor impairment using section III of the Unified Parkinson’s Disease Rating Scale (UPDRS); lower-limb functional strength using the Five Times Sit-to-Stand Test (5xSTS); and global cognitive function using the Montreal Cognitive Assessment (MoCA). Functionality and disability were assessed using the World Health Organization Disability Assessment Schedule 2.0 (WHODAS). Sociodemographic, cognitive, motor, mood, and functional disability variables were described using descriptive statistics. WHODAS and MoCA scores were converted to percentages of the maximum score and compared using the Friedman test, followed by paired Wilcoxon tests with Bonferroni correction. Associations between cognition, motor function, mood, and functional disability were analyzed using hierarchical multiple linear regression with standardized predictors. Results: The most impaired cognitive domains were delayed recall and language (p < 0.001). In the BESTest, greater deficits were observed in postural responses and anticipatory adjustments. Functional disability was more pronounced in the cognition and activities of daily living domains of the WHODAS (p < 0.001). Worse cognitive performance was associated with greater functional disability, particularly in self-reported cognition, self-care, and social participation (p < 0.05). Motor function showed an independent association with global disability and with the mobility and activities of daily living domains (p < 0.001), and was the main predictor of global disability in the adjusted models. Conclusion: Functional disability in AD results from the interaction between cognition and motor function. Motor deficits may also act as sensitive indicators of functional limitation even in mild to moderate stages, highlighting the need for assessment and therapeutic approaches that integrate cognitive and motor aspects in the clinical management of the disease.