title: Do muscle mass, muscle density, strength, and physical function similarly influence risk of hospitalization in older adults?
abstract: OBJECTIVE
  To examine the association between strength, function, lean mass, muscle density, and risk of hospitalization.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  Two U.S. clinical centers.
  
  
  METHODS
  Adults aged 70 to 80 (N=3,011) from the Health, Aging and Body Composition Study.
  
  
  METHODS
  Measurements were of grip strength, knee extension strength, lean mass, walking speed, and chair stand pace. Thigh computed tomography scans assessed muscle area and density (a proxy for muscle fat infiltration). Hospitalizations were confirmed by local review of medical records. Negative binomial regression models estimated incident rate ratios (IRRs) of hospitalization for race- and sex-specific quartiles of each muscle and function parameter separately. Multivariate models adjusted for age, body mass index, health status, and coexisting medical conditions.
  
  
  RESULTS
  During an average 4.7 years of follow-up, 1,678 (55.7%) participants experienced one or more hospitalizations. Participants in the lowest quartile of muscle density were more likely to be subsequently hospitalized (multivariate IRR=1.47, 95% confidence interval (CI)=1.24-1.73) than those in the highest quartile. Similarly, participants with the weakest grip strength were at greater risk of hospitalization (multivariate IRR=1.52, 95% CI=1.30-1.78, Q1 vs. Q4). Comparable results were seen for knee strength, walking pace, and chair stands pace. Lean mass and muscle area were not associated with risk of hospitalization.
  
  
  CONCLUSIONS
  Weak strength, poor function, and low muscle density, but not muscle size or lean mass, were associated with greater risk of hospitalization. Interventions to reduce the disease burden associated with sarcopenia should focus on increasing muscle strength and improving physical function rather than simply increasing lean mass.
authors.affiliation: Research Institute, California Pacific Medical Center, San Francisco, California 94107, USA. pcawthon@sfcc-cpmc.net
authors.forename: Peggy Mannen
authors.initials: PM
authors.lastname: Cawthon
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Fox
authors.forename: Shravanthi R
authors.initials: SR
authors.lastname: Gandra
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Delmonico
authors.forename: Chiun-Fang
authors.initials: CF
authors.lastname: Chiou
authors.forename: Mary S
authors.initials: MS
authors.lastname: Anthony
authors.forename: Ase
authors.initials: A
authors.lastname: Sewall
authors.forename: Bret
authors.initials: B
authors.lastname: Goodpaster
authors.forename: Suzanne
authors.initials: S
authors.lastname: Satterfield
authors.forename: Steven R
authors.initials: SR
authors.lastname: Cummings
authors.forename: Tamara B
authors.initials: TB
authors.lastname: Harris
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D000369:Aged, 80 and over; D001823:Body Composition / Q000502:physiology*; D005260:Female; D015577:Geriatric Assessment; D018737:Hand Strength / Q000502:physiology; D006760:Hospitalization; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D008297:Male; D006278:Medicare; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology* / Q000503:physiopathology; D016012:Poisson Distribution; D011446:Prospective Studies; D012044:Regression Analysis; D012306:Risk; D013848:Thigh; D014057:Tomography, X-Ray Computed; D019415:Torque; D014481:United States; D016138:Walking / Q000502:physiology*
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