title: Muscle mass index as a predictor of longevity in older adults.
abstract: OBJECTIVE
  Obesity (as defined by body mass index) has not been associated consistently with higher mortality in older adults. However, total body mass includes fat and muscle, which have different metabolic effects. This study was designed to test the hypothesis that greater muscle mass in older adults is associated with lower all-cause mortality.
  
  
  METHODS
  All-cause mortality was analyzed by the year 2004 in 3659 participants from the National Health and Nutrition Examination Survey III who were aged 55 years or more (65 years if women) at the time of the survey (1988-1994). Individuals who were underweight or died in the first 2 years of follow-up were excluded to remove frail elders from the sample. Skeletal muscle mass was measured using bioelectrical impedance, and muscle mass index was defined as muscle mass divided by height squared. Modified Poisson regression and proportional hazards regression were used to examine the relationship of muscle mass index with all-cause mortality risk and rate, respectively, adjusted for central obesity (waist hip ratio) and other significant covariates.
  
  
  RESULTS
  In adjusted analyses, total mortality was significantly lower in the fourth quartile of muscle mass index compared with the first quartile: adjusted risk ratio 0.81 (95% confidence interval, 0.71-0.91) and adjusted hazard ratio 0.80 (95% confidence interval, 0.66-0.97).
  
  
  CONCLUSIONS
  This study demonstrates the survival predication ability of relative muscle mass and highlights the need to look beyond total body mass in assessing the health of older adults.
authors.affiliation: Division of Endocrinology, Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, Calif. Electronic address: psrikanthan@mednet.ucla.edu.
authors.forename: Preethi
authors.initials: P
authors.lastname: Srikanthan
authors.affiliation: Division of Geriatrics, Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, Calif.
authors.forename: Arun S
authors.initials: AS
authors.lastname: Karlamangla
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001823:Body Composition; D015992:Body Mass Index; D017097:Electric Impedance; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016015:Logistic Models; D008136:Longevity; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000033:anatomy & histology*; D009749:Nutrition Surveys; D056128:Obesity, Abdominal / Q000401:mortality; D016012:Poisson Distribution; D016016:Proportional Hazards Models; D012306:Risk; D014481:United States / Q000453:epidemiology
keywords: Mortality; Muscle