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


METHODS
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 (ALMBMI), and ALM adjusted for height squared (ALMH2) 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.


RESULTS
For low lean mass, the cutpoints based on ALMBMI (<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).


CONCLUSIONS
Low lean mass defined by ALMBMI 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.
Department of Medicine, Research Centre of Heart, Brain, Hormone & Healthy Aging, Pharmacogenomics and Precision Therapeutics Laboratory, Department of Pharmacology and Pharmacy, Centre for Genomic Sciences, The State Key Laboratory of Pharmaceutical Biotechnology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam. lung1212@hku.hk.
Ching-Lung
CL
Cheung
Department of Medicine, Research Centre of Heart, Brain, Hormone & Healthy Aging, The State Key Laboratory of Pharmaceutical Biotechnology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam.
Karen S L
KS
Lam
Department of Medicine, Research Centre of Heart, Brain, Hormone & Healthy Aging, The State Key Laboratory of Pharmaceutical Biotechnology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam.
Bernard M Y
BM
Cheung
D000368:Aged; D000375:Aging / Q000502:physiology*; D000886:Anthropometry / Q000379:methods; D015992:Body Mass Index; D015986:Confounding Factors, Epidemiologic; D005260:Female; D005684:Gait; D015577:Geriatric Assessment / Q000379:methods; D006723:Hong Kong; D006801:Humans; D008297:Male; D051346:Mobility Limitation; D053580:Muscle Strength; D009749:Nutrition Surveys; D011237:Predictive Value of Tests; D016016:Proportional Hazards Models; D018570:Risk Assessment / Q000379:methods; D055948:Sarcopenia / Q000175:diagnosis / Q000401:mortality / Q000503:physiopathology
Body composition; Gait; Sarcopenia