Sarcopenia Definition & Outcomes Consortium Defined Low Grip Strength in Two Cross-Sectional, Population-Based Cohorts.

BACKGROUND/OBJECTIVES The extent to which the prevalence of muscle weakness in the US population varies by different putative grip strength constructs developed by the Sarcopenia Definitions and Outcomes Consortium (SDOC) has not been described. DESIGN Cross-sectional analysis. SETTING Two nationally representative cohorts-2010 and 2012 waves of the Health and Retirement Survey and round 1 (2011) of the National Health and Aging Trends Survey. PARTICIPANTS Adults aged 65 years and older (n = 12,984) were included in these analyses. MEASUREMENTS We analyzed three constructs of muscle weakness developed by the SDOC, and found to be associated with mobility disability for men and women, respectively: absolute grip strength (<35.5 kg and 20 kg); grip strength standardized to body mass index (<1.05 kg/kg/m² and 0.79 kg/kg/m²); and grip strength standardized to weight (<0.45 kg/kg and 0.337 kg/kg). We estimated the prevalence of muscle weakness defined by each of these constructs in the overall older US population, and by age, sex, race, and ethnicity. We also estimated the sensitivity and specificity of each of the grip strength constructs to discriminate slowness (gait speed <0.8 m/s) in these samples. RESULTS The prevalence of muscle weakness ranged from 23% to 61% for men and from 30% to 66% for women, depending on the construct used. There was substantial variation in the prevalence of muscle weakness by race and ethnicity. The sensitivity and specificity of these measures for discriminating slowness varied widely, ranging from 0.30 to 0.92 (sensitivity) and from 0.17 to 0.88 (specificity). CONCLUSIONS The prevalence of muscle weakness, defined by the putative SDOC grip strength constructs, depends on the construct of weakness used.