Cut Points for Clinical Muscle Weakness Among Older Americans

Introduction: Muscle weakness is an important indicator of disability, chronic disease, and early mortality. Grip strength is a simple, cost-effective measure of overall muscle strength. The Foundation of the National Institutes of Health recently proposed sex-specific grip strength cut points for clinical muscle weakness. However, these criteria were established using non - nationally representative data. This study used nationally representative data on Americans aged >= 65 years to identify race-and sex-specific cut points for clinical muscle weakness and quantify prevalence among older blacks and whites by sex. Methods: Classification and Regression Tree models were used to identify cut points based on individual-level grip strength associated with slow gait speed (< 0.8 m/second) among 7,688 individuals (57% female; 8% black; mean age, 74.6 [SD = 6.79] years) from the 2010/2012 Health and Retirement Study during January - April 2016. Identified cut points were then used to quantify the prevalence of weakness by race/sex subgroup. Results: Fifty-five percent of men (maximum grip strength < 39 kg) and 47% of women (maximum grip strength < 22 kg) were classified as weak. Higher cut points were identified for black men (maximum grip strength < 40 kg) and women (maximum grip strength < 31 kg), and the prevalence of weakness (57% and 88%, respectively) was higher compared with whites. Fifty-five percent of individuals had slow gait speed (< 0.8 m/second). Conclusions: Prevalence of weakness was substantially higher than previous reports, underscoring the importance of using population-level data to identify individuals at greatest risk for adverse health outcomes. This is the first study to establish cut points for muscle weakness in a nationally representative sample by race and sex. (C) 2017 American Journal of Preventive Medicine. Published by Elsevier Inc. All rights reserved.