Distinct mobility facets and their association with intrinsic capacity domains in (pre-)frail community-dwelling older adults: an application of the unified framework for measuring mobility

Maintaining mobility is essential for healthy aging. A recently proposed unified framework conceptualizes mobility through three facets: actual mobility, perceived mobility, and locomotor capacity. Identifying determinants of each facet is important for understanding mobility and informing tailored mobility-focused interventions. This is particularly relevant for (pre-)frail older adults, who are especially vulnerable to mobility decline. The aim of this study was to examine associations of the three mobility facets with intrinsic capacity (IC) domains and environmental factors in this population. This cross-sectional study used baseline data from 385 (pre-)frail community-dwelling older participants (81.2 ± 5.9 years, 73.5% women) of the randomized controlled PromeTheus trial. Actual mobility was assessed with the Life-Space Assessment, perceived mobility with the function component of the Late-Life Function & Disability Instrument, and locomotor capacity with the Short Physical Performance Battery (lower extremity function). Other IC domains included vitality (fatigue, nutritional status, handgrip strength), psychological (concerns about falling, global affect, loneliness), sensory (sensory index based on specialist visits), and cognitive (global function) capacities. Environmental factors comprised living situation, social network, city size, and weather conditions. Bivariate analyses identified candidate variables for multivariable linear regression models, adjusted for demographic and clinical characteristics. In the multivariable analyses, actual mobility was positively associated with lower extremity function, nutritional status, social network, and sunshine duration. Perceived mobility was positively associated with lower extremity function, handgrip strength, city size, and negatively with concerns about falling. Locomotor capacity was positively associated with handgrip strength, cognitive function, city size, and cohabitation, and negatively with concerns about falling. The study revealed shared and facet-specific associations of actual mobility, perceived mobility, and locomotor capacity with IC domains and environmental factors. These findings highlight the multifactorial nature of mobility and may inform mobility-focused interventions that consider both shared and facet-specific determinants in (pre-)frail community-dwelling older adults. German Clinical Trials Register (DRKS00024638); prospectively registered on March 11, 2021.