What age trajectories of cumulative deficits and medical costs tell us about individual aging and mortality risk: Findings from the NLTCS-Medicare data.

An important feature of aging-related deterioration in human health is the decline in organisms' resistance to stresses, which contributes to an increase in morbidity and mortality risks. In human longitudinal studies of aging, such a decline is not measured directly, so indirect methods of statistical modeling have to be used for evaluating this characteristic. Since medical interventions reflect severity of occurring health disorders, data from Medicare service use files can be used for such modeling. In this paper, we use the National Long Term Care Survey (NLTCS) data merged with the Medicare service use files to investigate dynamics of stress resistance in the U.S. elderly. We constructed individual indices of cumulative deficits and medical costs and investigated their separate and joint effects on dynamics of mortality risks using the quadratic hazard model (QHM). We found that males show a faster decline in stress resistance with age than females.