Evaluation of Cutpoints for Low Lean Mass and Slow Gait Speed in Predicting Death in the National Health and Nutrition Examination Survey 1999-2004

Sarcopenia is commonly defined as loss of muscle mass with limited muscle function or strength. Different cutpoints of low lean mass and slow gait speed have been proposed by different professional working groups. We compared the performance of different cutpoints of low lean mass and slow gait speed in predicting death. We analyzed data of participants aged 65 years or older from the continuous National Health and Nutrition Examination Survey 1999-2004 (N = 2,841), and the subsequent follow-up data on mortality up to December 31, 2006. For low lean mass, cutpoints based on appendicular lean mass (ALM) alone, ALM adjusted for body mass index (ALM(BMI)), and ALM adjusted for height squared (ALM(H2)) were evaluated. For slow gait speed, the cutpoints based on 0.8 and 1.0 m/s were evaluated. A Cox-proportional hazard regression model with adjustment for multiple confounding factors was used for the association analyses. For low lean mass, the cutpoints based on ALM(BMI) (< 0.512 in women and < 0.789 in men) showed the most significant association and highest hazard ratio with death (hazard ratio = 1.72; 95% CI: 1.28-2.29). For slow gait speed, all cutpoints tested showed significant association with death in the full model ( p < .001), while the cutpoint 0.8 m/s showed the highest hazard ratio (2.32; 95% CI: 1.58-3.39). Low lean mass defined by ALM(BMI) showed the strongest association with death; while slow gait speed showed significant association with death, with the strongest association being observed for the cutpoint of 0.8 m/s. Further studies validating the cutpoints are warranted before using them in clinical settings.