Health decline, aging and mortality: how are they related?

Abstract

The deterioration of human health with age is manifested in changes of thousands of physiological and biological variables. The contribution of some of such changes to the mortality risk may be small and cannot be reliably detected by existing statistical methods. A cumulative index of health/wellbeing disorders, which counts changes in observed variables on the way of losing health, may be an appropriate way to take the effects of such variables into account. In this paper we investigate regularities of the aging-related changes in human health/well-being/survival status described by such an index using the new version of the quadratic hazard model of human aging and mortality. We found that the shape and the location of the mortality risk, considered as a function of the introduced health-related index, changes with age reflecting the decline in stress resistance and the age-dependence of the "optimal" health/well-being status. Comparison of these results with findings from early studies using the Cox's-like model of risk function indicates that the results are likely to describe regularities of deterioration in human health during the aging process.

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

“…This may characterize behavioral adaptation of those who already have some disorders, or trade-off between chronic conditions. In 2007c) we discuss possible causes of non-zero f t . For this reason, we consider a general case with non-zero f t for the MCI as well.…”

“…To make the results of this study comparable with those obtained in 2007c), we constructed the DI using the same subset of deficits (32 questions from the NLTCS detailed questionnaires). This subset is mostly similar to those assessed from the Canadian Study of Health and Aging (Mitnitski et al, 2001).…”

“…It includes: difficulty with eating, dressing, walking around, getting in/out bed, getting bath, toileting, using telephone, going out, shopping, cooking, light house work, taking medicine, managing money, arthritis, Parkinson's disease, glaucoma, diabetes, stomach problem, history of heart attack, hypertension, history of stroke, flu, broken hip, broken bones, trouble with bladder/bowels, dementia, self-rated health, as well as problems with vision, hearing, ear, teeth, and feet. As in early works 2007c), all these deficits are assessed in five waves of the NLTCS. Following Mitnitski et al (Mitnitski et al, 2001), we defined the DI as an unweighted count of the number of such deficits divided by the total number of all potential deficits considered for a given person.…”

“…These data allow for constructing the index of cumulative deficits, DI, (also called the frailty index) which seems to be a useful indicator of health/well-being deterioration Mitnitski and Rockwood, 2006;Mitnitski et al, 2004;Rockwood et al, 2006;. The properties of such index constructed from the NLTCS data were studied by Kulminski et al (2007a; and Yashin et al (2007b;2007c). The results of these studies showed that the DI is a convenient index describing aging-related health/well-being deterioration in the U.S. elderly.…”

“…We use the width of the U-shaped risk function as a measure of resistance to stress associated with a factor specifying such risk. In these analyses, we used three versions of the stochastic process model of human mortality and aging 2007c).…”