Physiological Redundancy in Older Adults in Relation to the Change with Age in the Slope of a Frailty Index

Abstract

OBJECTIVES:To test the proposition, using routinely available clinical data, that deficit accumulation results in loss of redundancy. In keeping with the reliability theory of aging, this would be quantitated by attenuation in the slope of a Frailty Index (FI) with age. The more deficits, the less steep the slope and the less redundancy. DESIGN: Cross-sectional analysis of a prospective cohort study, with 5-year mortality data. SETTING: The clinical sample of the second wave of the Canadian Study of Health and Aging. PARTICIPANTS: Two thousand three hundred five people aged 70 and older at baseline. MEASUREMENTS: A FI based on data used for a Comprehensive Geriatric Assessment (CGA), the slope of the relationship between age and the FI-CGA, the limit value of the FI-CGA, mortality. RESULTS: An age-invariant limit to deficit accumulation was demonstrated; the observed 99% limit was 0.66. At the 25th percentile of deficit accumulation (FI-CGA $ 0.18), the slope of the FI-CGA in relation to age was 0.044 (range 0.038-0.049). When deficits had increased to 75% of the maximum value (FI-CGA $ 0.52), the slope fell to 0.021 (range 0.016-0.027). By the 85th percentile (FI-CGA $ 0.6), the slope had become statistically indistinguishable from 0. CONCLUSION: As predicted by the reliability theory of aging, the rate of deficit accumulation slows with increasing frailty. A FI derived from data routinely collected as part of a CGA can in this way quantify loss of redundancy in older adults. Quantifying loss of redundancy can aid clinical decision-making; its application to individual prognostication in clinical samples warrants further evaluation. J Am Geriatr Soc 58:318-323, 2010.

Assessing Balance and Mobility to Track Illness and Recovery in Older Inpatients

“…Here, frailty status affected both time to recovery and recovery potential. This is consistent with other observations of the impact of frailty on both the presentation 6 and outcomes 35 of acute illness in older people. Compared to illness severity scores, frailty is more strongly associated with death 36 and functional decline 37 after acute illness.…”

“…40 In a frail person, as a complex system close to failure, any acute illness can manifest as worsened balance and mobility. 35,40 Our data must be interpreted with caution. Patients were recruited from a single hospital, the sample size is modest and small numbers of patients died.…”

“…Although frailty is measured in different ways, 30 people who are frail have a diminished capacity to effectively compensate for external stressors and to prevent further declines associated with aging and mortality. 35,38 The HABAM scores in these patients showed different trajectories according to FI-CGA score: frailer patients tended to have slower rates of recovery and lower levels of performance both on admission and after 2 weeks in hospital. In this way, the FI-CGA may be a clinically feasible means to measure patients' capacity to respond to acute illness.…”

“…39 As deficits accumulate, redundancy is lost, resulting in a reduced ability to withstand stresses. 35 As any complex system fails, the first processes to be compromised are those that require coordinated, integrated and precise interactions between many components. In humans, such high-order functions notably include upright bipedal ambulation.…”

Aging, frailty and age-related diseases

“…The term ''frailty'' is commonly used in different ways under different circumstances but mainly to describe a physical and functional decline which may occur as a consequence of certain diseases, but most intriguingly also in the absence of identifiable specific disease (Kanapuru and Ershler 2009). Thus, frailty is viewed as a physiologic loss of reserves and resilience (Rockwood and Mitnitski 2007a, b;Fried et al 2009;Rockwood et al 2010).…”