title: Relative fitness and frailty of elderly men and women in developed countries and their relationship with mortality.
abstract: OBJECTIVE
  To investigate the relationship between accumulated health-related problems (deficits), which define a frailty index in older adults, and mortality in population-based and clinical/institutional-based samples.
  
  
  METHODS
  Cross-sectional and cohort studies.
  
  
  METHODS
  Seven population-based and four clinical/institutional surveys in four developed countries.
  
  
  METHODS
  Thirty-six thousand four hundred twenty-four people (58.5% women) aged 65 and older.
  
  
  METHODS
  A frailty index was constructed as a proportion of all potential deficits (symptoms, signs, laboratory abnormalities, disabilities) expressed in a given individual. Relative frailty is defined as a proportion of deficits greater than average for age. Measures of deficits differed across the countries but included common elements.
  
  
  RESULTS
  In each country, community-dwelling elderly people accumulated deficits at about 3% per year. By contrast, people from clinical/institutional samples showed no relationship between frailty and age. Relative fitness/frailty in both sexes was highly correlated (correlation coefficient >0.95, P<.001) with mortality, although women, at any given age, were frailer and had lower mortality. On average, each unit increase in deficits increased by 4% the hazard rate for mortality (95% confidence interval=0.02-0.06).
  
  
  CONCLUSIONS
  Relative fitness and frailty can be defined in relation to deficit accumulation. In population studies from developed countries, deficit accumulation is robustly associated with mortality and with age. In samples (e.g., clinical/institutional) in which most people are frail, there is no relationship with age, suggesting that there are maximal values of deficit accumulation beyond which survival is unlikely.
authors.affiliation: Department of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada.
authors.forename: Arnold
authors.initials: A
authors.lastname: Mitnitski
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Song
authors.forename: Ingmar
authors.initials: I
authors.lastname: Skoog
authors.forename: G A
authors.initials: GA
authors.lastname: Broe
authors.forename: Jafna L
authors.initials: JL
authors.lastname: Cox
authors.forename: Eva
authors.initials: E
authors.lastname: Grunfeld
authors.forename: Kenneth
authors.initials: K
authors.lastname: Rockwood
mesh_terms: D017677:Age Distribution; D000368:Aged; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D019049:Developed Countries; D005260:Female; D016330:Frail Elderly / Q000706:statistics & numerical data*; D015577:Geriatric Assessment; D006304:Health Status; D006801:Humans; D008297:Male; D009026:Mortality; D015999:Multivariate Analysis; D010809:Physical Fitness; D016016:Proportional Hazards Models; D017678:Sex Distribution