Biometrics





    

TheScientificWorldJOURNAL (ISSN 1537-744X)

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  Title: The Accumulation of Deficits with Age and Possible Invariants of Aging
  Authors:   Mitnitski, Arnold B.; Mogilner, Alexander J.; MacKnight, Chris ; Rockwood, Kenneth  
  Journal:   TheScientificWorldJOURNAL  
  Year:   2002  
  Volume:   2  
  Page Range:   1816-1822  
  Article Type:   Short Communication  
  Domains:    Aging ,  Medical Care ,  Biophysics ,  Development & Embryology  
  DOI:   10.1100/tsw.2002.861  
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  Keywords:   aging, disability, frailty, frailty index, frailty trajectories, gender difference, compensation law, Gompertz-Makeham law, invariants of aging, biological constants, macroparameters, National Population Health Survey, databases, mathematical modeling  
     
 
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      Abstract  
      This paper extends a method of apprising health status to a broad range of ages from adolescence to old age. The “frailty index” is based on the accumulation of deficits (symptoms, signs, disease classifications) as analyzed in the National Population Health Survey, a representative Canadian population sample (n = 81,859). The accumulation of deficits has both an age-independent (background) component and an age-dependent (exponential) component, akin to the well-known Gompertz-Makeham model for the risk of mortality. While women accumulate more deficits than men of the same age, on average, their rate of accumulation is lower, so the difference in the level of deficits between men and women decreases with age. Two possible invariants of the process of accumulation of deficits were found: (1) the age at which the average proportion of deficits coincides for men and women is 94 years, which closely matches the species-specific lifespan in humans (95 ± 2); (2) the value of the frailty index (proportion of deficits), which corresponds to that age (0.18). The similarity between mortality kinetics and the accumulation of deficits (frailty kinetics), and the coincidence of the time parameters in the frailty and mortality models make it possible to express mortality risk in terms of accumulated deficits. This provides a simple and accessible tool that might have potential in a number of biomedical applications.  
     
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