title: Alternative definitions of sarcopenia, lower extremity performance, and functional impairment with aging in older men and women.
abstract: OBJECTIVE
  To compare two methods for classifying an individual as sarcopenic for predicting decline in physical function in the Health, Aging and Body Composition Study.
  
  
  METHODS
  Observational cohort study with 5 years of follow-up.
  
  
  METHODS
  Communities in Memphis, Tennessee, and Pittsburgh, Pennsylvania.
  
  
  METHODS
  Men and women aged 70 to 79 (N=2,976, 52% women, 41% black).
  
  
  METHODS
  Appendicular lean mass (aLM) was measured using dual energy x-ray absorptiometry, and participants were classified as sarcopenic first using aLM divided by height squared and then using aLM adjusted for height and body fat mass (residuals). Incidence of persistent lower extremity limitation (PLL) was measured according to self-report, and change in objective lower extremity performance (LEP) measures were observed using the Short Physical Performance Battery.
  
  
  RESULTS
  There was a greater risk of incident PLL in women who were sarcopenic using the residuals sarcopenia method than in women who were not sarcopenic (hazard ratio (HR)=1.34, 95% confidence interval (CI)=1.11-1.61) but not in men. Those defined as sarcopenic using the aLM/ht(2) method had lower incident PLL than nonsarcopenic men (HR=0.76, 95% CI=0.60-0.96) and women (HR=0.75, 95% CI=0.60-0.93), but these were no longer significant with adjustment for body fat mass. Using the residuals method, there were significantly poorer LEP scores in sarcopenic men and women at baseline and Year 6 and greater 5-year decline, whereas sarcopenic men defined using the aLM/ht(2) method had lower 5-year decline. Additional adjustment for fat mass attenuated this protective effect.
  
  
  CONCLUSIONS
  These findings suggest that sarcopenia defined using the residuals method, a method that considers height and fat mass together, is better for predicting disability in an individual than the aLM/ht(2) method, because it considers fat as part of the definition.
authors.affiliation: Department of Epidemiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA. delmonicom@edc.pitt.edu
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Delmonico
authors.forename: Tamara B
authors.initials: TB
authors.lastname: Harris
authors.forename: Jung-Sun
authors.initials: JS
authors.lastname: Lee
authors.forename: Marjolein
authors.initials: M
authors.lastname: Visser
authors.forename: Michael
authors.initials: M
authors.lastname: Nevitt
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Kritchevsky
authors.forename: Frances A
authors.initials: FA
authors.lastname: Tylavsky
authors.forename: Anne B
authors.initials: AB
authors.lastname: Newman
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D000375:Aging / Q000502:physiology*; D001827:Body Height; D015992:Body Mass Index; D005260:Female; D005684:Gait; D006801:Humans; D035002:Lower Extremity / Q000503:physiopathology*; D008297:Male; D051346:Mobility Limitation; D009133:Muscular Atrophy / Q000473:pathology; D004856:Postural Balance; D013851:Thinness