Alexander J. Mogilner

Bio: Alexander J. Mogilner is an academic researcher from Dalhousie University. The author has contributed to research in topics: Dementia & Population. The author has an hindex of 10, co-authored 13 publications receiving 2548 citations.

Accumulation of deficits as a proxy measure of aging.

Abstract: This paper develops a method for appraising health status in elderly people. A frailty index was defined as the proportion of accumulated deficits (symptoms, signs, functional impairments, and laboratory abnormalities). It serves as an individual state variable, reflecting severity of illness and proximity to death. In a representative database of elderly Canadians we found that deficits accumulated at 3% per year, and show a gamma distribution, typical for systems with redundant components that can be used in case of failure of a given subsystem. Of note, the slope of the index is insensitive to the individual nature of the deficits, and serves as an important prognostic factor for life expectancy. The formula for estimating an individual's life span given the frailty index value is presented. For different patterns of cognitive impairments the average within-group index value increases with the severity of the cognitive impairment, and the relative variability of the index is significantly reduced. Finally, the statistical distribution of the frailty index sharply differs between well groups (gamma distribution) and morbid groups (normal distribution). This pattern reflects an increase in uncompensated deficits in impaired organisms, which would lead to illness of various etiologies, and ultimately to increased mortality. The accumulation of deficits is as an example of a macroscopic variable, i.e., one that reflects general properties of aging at the level of the whole organism rather than any given functional deficiency. In consequence, we propose that it may be used as a proxy measure of aging.

Frailty, fitness and late-life mortality in relation to chronological and biological age.

Abstract: People age at remarkably different rates, but how to estimate trajectories of senescence is controversial. In a secondary analysis of a representative cohort of Canadians aged 65 and over (n = 2914) we estimated a frailty index based on the proportion of 20 deficits observed in a structured clinical examination. The construct validity of the index was examined through its relationship to chronological age (CA). The criterion validity was examined in its ability to predict mortality, and in relation to other predictions about aging. From the frailty index, relative (to CA) fitness and frailty were estimated, as was an individual's biological age. The average value of the frailty index increased with age in a log-linear relationship (r = 0.91; p < 0.001). In a Cox regression analysis, biological age was significantly more highly associated with death than chronological age. The average increase in the frailty index (i.e. the average accumulation of deficits) amongst those with no cognitive impairment was 3 per cent per year. The frailty index is a sensitive predictor of survival. As the index includes items not traditionally related to adverse health outcomes, the finding is compatible with a view of frailty as the failure to integrate the complex responses required to maintain function.

The Accumulation of Deficits with Age and Possible Invariants of Aging

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.

A global clinical measure of fitness and frailty in elderly people

Abstract: Background: There is no single generally accepted clinical definition of frailty. Previously developed tools to assess frailty that have been shown to be predictive of death or need for entry into an institutional facility have not gained acceptance among practising clinicians. We aimed to develop a tool that would be both predictive and easy to use. Methods: We developed the 7-point Clinical Frailty Scale and applied it and other established tools that measure frailty to 2305 elderly patients who participated in the second stage of the Canadian Study of Health and Aging (CSHA). We followed this cohort prospectively; after 5 years, we determined the ability of the Clinical Frailty Scale to predict death or need for institutional care, and correlated the results with those obtained from other established tools. Results: The CSHA Clinical Frailty Scale was highly correlated ( r = 0.80) with the Frailty Index. Each 1-category increment of our scale significantly increased the medium-term risks of death (21.2% within about 70 mo, 95% confidence interval [CI] 12.5%–30.6%) and entry into an institution (23.9%, 95% CI 8.8%–41.2%) in multivariable models that adjusted for age, sex and education. Analyses of receiver operating characteristic curves showed that our Clinical Frailty Scale performed better than measures of cognition, function or comorbidity in assessing risk for death (area under the curve 0.77 for 18-month and 0.70 for 70-month mortality). Interpretation: Frailty is a valid and clinically important construct that is recognizable by physicians. Clinical judgments about frailty can yield useful predictive information.

A standard procedure for creating a frailty index

Abstract: Background Frailty can be measured in relation to the accumulation of deficits using a frailty index. A frailty index can be developed from most ageing databases. Our objective is to systematically describe a standard procedure for constructing a frailty index.

Prevalence of Frailty in Community-Dwelling Older Persons: A Systematic Review

Abstract: Objectives To systematically compare and pool the prevalence of frailty, including prefrailty, reported in community-dwelling older people overall and according to sex, age, and definition of frailty used. Design Systematic review of the literature using the key words elderly, aged, frailty, prevalence, and epidemiology. Setting Cross-sectional data from community-based cohorts. Participants Community-dwelling adults aged 65 and older. Measurements In the studies that were found, frailty and prefrailty were measured according to physical phenotype and broad phenotype, the first defining frailty as a purely physical condition and the second also including psychosocial aspects. Results Reported prevalence in the community varies enormously (range 4.0–59.1%). The overall weighted prevalence of frailty was 10.7% (95% confidence interval (CI) = 10.5–10.9; 21 studies; 61,500 participants). The weighted prevalence was 9.9% for physical frailty (95% CI = 9.6–10.2; 15 studies; 44,894 participants) and 13.6% for the broad phenotype of frailty (95% CI = 13.2–14.0; 8 studies; 24,072 participants) (chi-square (χ2) = 217.7, degrees of freedom (df)=1, P < .001). Prevalence increased with age (χ2 = 6067, df = 1, P < .001) and was higher in women (9.6%, 95% CI = 9.2–10.0%) than in men (5.2%, 95% CI = 4.9–5.5%; χ2 = 298.9 df = 1, P < .001). Conclusion Frailty is common in later life, but different operationalization of frailty status results in widely differing prevalence between studies. Improving the comparability of epidemiological and clinical studies constitutes an important step forward.

Frailty in Relation to the Accumulation of Deficits

Abstract: This review article summarizes how frailty can be considered in relation to deficit accumulation. Recalling that frailty is an age-associated, nonspecific vulnerability, we consider symptoms, signs, diseases, and disabilities as deficits, which are combined in a frailty index. An individual's frailty index score reflects the proportion of potential deficits present in that person, and indicates the likelihood that frailty is present. Although based on a simple count, the frailty index shows several interesting properties, including a characteristic rate of accumulation, a submaximal limit, and characteristic changes with age in its distribution. The frailty index, as a state variable, is able to quantitatively summarize vulnerability. Future studies include the application of network analyses and stochastic analytical techniques to the evaluation of the frailty index and the description of other state variables in relation to frailty.