Muscle weakness and functional limitations in an ethnically diverse sample of older adults

Objectives: Muscle weakness is often linked to functional limitations in older adults. However, certain demographic characteristics, such as ethnicity, may differentially impact the association between weakness and functional limitations. This investigation sought to (1) identify sex- and ethnically-specific muscle weakness thresholds associated with functional limitations among older adults, and (2) determine the odds of functional limitations for each ethnicity by sex after identifying older adults below the weakness thresholds. Design: Persons aged >= 60 years from the 2011-2012 to 2013-2014 waves of the National Health and Nutrition Examination Survey identifying as non-Hispanic white, non-Hispanic black, Hispanic, or non-Hispanic Asian were included. Handgrip strength was normalized to each participant's body weight (normalized grip strength (NGS)). Participants responded to 19-items asking them about their ability to perform certain activities of daily living, instrumental activities of daily living, leisure and social activities, lower extremity mobility functions, and general physical activities. Receiver operating characteristic curves identified the optimal NGS thresholds associated with functional limitations. Covariate-adjusted multiple logistic regression models were performed to determine the odds of functional limitations for weak vs. not-weak participants. Results: Of the 3,027 participants, the highest NGS thresholds for functional limitations were in non-Hispanic Asian males (0.41; p < 0.001) and Hispanic females (0.36; p < 0.001); whereas, the lowest NGS thresholds were in Hispanic males (0.25; p < 0.001) and non-Hispanic black females (0.23; p < 0.001). Weak non-Hispanic Asian males (odds ratio (OR): 10.42; 95% confidence interval (CI): 10.24, 10.61) and females (OR: 11.95; CI: 11.71, 12.19) had the highest odds for functional limitations compared to their non-weak counterparts. Conclusion: Preserving muscle strength, especially for certain older adult populations, may help reduce the odds of developing functional limitations. Interventions designed to increase muscle strength to preserve or improve function should consider the role of ethnicity when designing such interventions and identifying at risk populations.