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PubMed2005

Frailty in older Mexican Americans.

OBJECTIVES: To identify sociodemographic characteristics and health performance variables associated with frailty in older Mexican Americans. DESIGN: A prospective population-based survey. SETTING: Homes of older adults living in the southwest. PARTICIPANTS: Six hundred twenty-one noninstitutionalized Mexican-American men and women aged 70 and older included in the Hispanic Established Populations for Epidemiologic Study of the Elderly participated in a home-based interview. MEASUREMENTS: Interviews included information on sociodemographics, self-reports of medical conditions (arthritis, diabetes mellitus, heart attack, hip fracture, cancer, and stroke) and functional status. Weight and measures of lower and upper extremity muscle strength were obtained along with information on activities of daily living and instrumental activities of daily living. A summary measure of frailty was created based on weight loss, exhaustion, grip strength, and walking speed. Multivariable linear regression identified variables associated with frailty at baseline. Logistic regression examined variables predicting frailty at 1-year follow-up. RESULTS: Sex was associated with frailty at baseline (F=4.28, P=.03). Predictors of frailty in men included upper extremity strength, disability (activities of daily living), comorbidities, and mental status scores (Nagelkerke coefficient of determination (R(2))=0.37). Predictors for women included lower extremity strength, disability (activities of daily living), and body mass index (Nagelkerke R(2)=0.29). At 1-year follow-up, 83% of men and 79% of women were correctly classified as frail. CONCLUSION: Different variables were identified as statistically significant predictors of frailty in Mexican-American men and women aged 70 and older. The prevention, development, and treatment of frailty in older Mexican Americans may require consideration of the unique characteristics of this population.

Activities of Daily Living↗

PubMed2000

Conceptualisation and measurement of frailty in elderly people.

The use of the term 'frailty' has shown tremendous growth in the last 15 years, but this has not been accompanied by a widely accepted definition, let alone agreed-upon measures. In this paper, we review approaches to the definition and measurement of frailty and discuss the relationship between frailty, aging and disability. Two trends are evident in definitions, which often trade off comprehensiveness for precision: frailty can be seen as being synonymous with a single-system problem or as a multisystem problem. The essential feature of frailty is the notion of risk due to instability (itself suggesting a balance of many factors), and has been only poorly measured to date. Future models of frailty should incorporate more precise operationalisation of the probability of frailty and better explain the relationship between disease, disability and frailty.

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PubMed1998

Balance and muscle strength as predictors of frailty among older adults.

The term frailty is increasingly used in gerontological literature and in practice. However, indicators differentiating frail from nonfrail are not well delineated. Identifying factors discriminating between frail and nonfrail older community-residing adults may lead to more comprehensive clinical assessments and targeted interventions to minimize or prevent frailty. Eighty-four adults, ages 60 to 88 (mean = 74) living independently in the community completed a functional performance questionnaire and a perceived health questionnaire that were combined as measures of frailty. Predictor variables of frailty included four measures of balance and three measures of lower leg strength. Discriminant analysis revealed that one balance score and dorsiflexion correctly classified 65% of group membership, with better prediction of the nonfrail than frail group. This study clarifies that the predictors of frailty include the combination of dorsiflexion strength and balance, specifically the contribution of vision to balance when the support surface is compliant. Recommendations are proposed for conceptualizing and operationalizing frailty and adding variables to enhance discrimination between frailty and nonfrailty. Nursing implications include adding clinical assessments of specific components of balance and ankle strength to develop a more comprehensive evaluation of frailty.

Activities of Daily Living↗

PubMed2006

Frailty in the elderly: the physical dimension.

Frailty may be considered as a vulnerable status, which can precede the onset of overt disability. Operational definitions of frailty vary widely according to the conceptual framework: some authors consider frailty in a broad sense, which encompasses the physical, social, cognitive, psychological dimensions and comorbidity, whereas others define the syndrome more restrictively, mainly on the basis of performance parameters, such as gait speed, grip strength and physical activity. All these definitions are provided of a high predictive value for adverse outcomes, such as disability, hospitalization and mortality. Sarcopenia (i.e. the reduction of muscular mass and function) plays a predominant role in the pathogenesis of frailty. Among the factors responsible for sarcopenia (such as proinflammatory cytokines, low growth hormone and testosterone levels, increased production of oxygen free radicals, malnutrition and reduced neurological drive), immobility and lack of exercise have a preponderant role. Therefore, the diagnosis of frailty is mandatory for the early identification of a subset of elderly subjects at high risk, which can receive benefit from rehabilitation. A self-report and objective evaluation of physical performance are the best indicators of frailty in elderly subjects, a poor performance suggesting the need of an early and proper intervention. Structured exercise programs are effective in contrasting the progression of frailty, but an healthy and active lifestyle may be sufficient for delaying the onset of disability. In conclusion, there is clear evidence for prescription of exercise within the mainstream of the medical practice, rather than as an optional adjunct to standard care of the oldest old, given the public health implication of frailty, whose prevalence is going to increase in western populations.

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PubMed2002

Proportional hazards models with frailties and random effects.

We discuss some of the fundamental concepts underlying the development of frailty and random effects models in survival. One of these fundamental concepts was the idea of a frailty model where each subject has his or her own disposition to failure, their so-called frailty, additional to any effects we wish to quantify via regression. Although the concept of individual frailty can be of value when thinking about how data arise or when interpreting parameter estimates in the context of a fitted model, we argue that the concept is of limited practical value. Individual random effects (frailties), whenever detected, can be made to disappear by elementary model transformation. In consequence, unless we are to take some model form as unassailable, beyond challenge and carved in stone, and if we are to understand the term 'frailty' as referring to individual random effects, then frailty models have no value. Random effects models on the other hand, in which groups of individuals share some common effect, can be used to advantage. Even in this case however, if we are prepared to sacrifice some efficiency, we can avoid complex modelling by using the considerable power already provided by the stratified proportional hazards model. Stratified models and random effects models can both be seen to be particular cases of partially proportional hazards models, a view that gives further insight. The added structure of a random effects model, viewed as a stratified proportional hazards model with some added distributional constraints, will, for group sizes of five or more, provide no more than modest efficiency gains, even when the additional assumptions are exactly true. On the other hand, for moderate to large numbers of very small groups, of sizes two or three, the study of twins being a well known example, the efficiency gains of the random effects model can be far from negligible. For such applications, the case for using random effects models rather than the stratified model is strong. This is especially so in view of the good robustness properties of random effects models. Nonetheless, the simpler analysis, based upon the stratified model, remains valid, albeit making a less efficient use of resources.

Humans↗

PubMed2003

The heritability of cause-specific mortality: a correlated gamma-frailty model applied to mortality due to respiratory diseases in Danish twins born 1870-1930.

The genetic influence on susceptibility to diseases of the respiratory system and all-cause mortality was studied using data for identical (MZ) and fraternal (DZ) twins. Data from the Danish Twin Register include 1344 MZ and 2411 DZ male twin pairs and 1470 MZ and 2730 DZ female twin pairs born between 1870 and 1930, where both individuals were alive on 1 011943. We used the correlated gamma-frailty model. Proportions of variance in frailty attributable to genetic and environmental factors were assessed using the structural equation model approach. For all-cause mortality the correlation coefficients of frailty for MZ twins tend to be higher than for DZ twins. For mortality with respect to respiratory diseases this effect was only seen in females, whereas males showed the opposite effect. Five standard biometric models are fitted to the data to evaluate the magnitude and nature of genetic and environmental factors on mortality. Using the best fitting biometric model heritability for cause of death was found to be 0.58 (0.07) for all-cause mortality (AE-model) and zero for diseases of the respiratory system for males. Heritability was 0.63 (0.11) for all-cause mortality (DE-model) and 0.18 (0.09) for diseases of the respiratory system (DE-model) for females. The analysis confirms the presence of a strong genetic influence on individual frailty associated with all-cause mortality. For respiratory diseases, no genetic influence was found in males and only weak genetic influence in females. The nature of genetic influences on frailty with respect to all-cause mortality is probably additive in males and dominant in females, whereas for frailty with respect to deaths caused by respiratory diseases in females, there are genetic factors present which are caused by dominance. Environmental influences are non-shared with exception of frailty with respect to respiratory diseases in males, where the shared environment plays an important role.

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PubMed2006

Dispersion frailty models and HGLMs.

In medical research recurrent event times can be analysed using a frailty model in which the frailties for different individuals are independent and identically distributed. However, such a homogeneous assumption about frailties could sometimes be suspect. For modelling heterogeneity in frailties we describe dispersion frailty models arising from a new class of models, namely hierarchical generalized linear models. Using the kidney infection data we illustrate how to detect and model heterogeneity among frailties. Stratification of frailty models is also investigated.

Adult↗

PubMed2005

A comparison of different bivariate correlated frailty models and estimation strategies.

Frailty models are becoming increasingly popular in multivariate survival analysis. Shared frailty models in particular are often used despite their limitations. To overcome their disadvantages numerous correlated frailty models were established during the last decade. In the present study, we examine bivariate correlated frailty models, and especially the behavior of the parameter estimates when using different estimation strategies. We consider three different bivariate frailty models: the gamma model and two versions of the log-normal model. The traditional maximum likelihood procedure of parameter estimation in the gamma case with an explicit available likelihood function is compared with maximum likelihood methods based on numerical integration and a Bayesian approach using MCMC methods with the help of a comprehensive simulation study. We detected a strong dependence between the two parameter estimates (variance and correlation of frailties) in the bivariate correlated frailty model and analyzed this dependence in detail.

Bayes Theorem↗

PubMed2003

Frailty in the elderly: contributions of sarcopenia and visceral protein depletion.

In any given population of free-living individuals 65 years of age and older, a substantial proportion (in the range of 6% to 25%) suffers from many of the elements of the syndrome of frailty. Although the syndrome is complex and still lacks a standard definition, there is a growing consensus about the signs and symptoms as well as the pattern of biological correlates that characterize this disorder. Patients who are afflicted with frailty typically exhibit loss of muscle strength, fatigue easily, are physically inactive, and have a slow-and often unsteady-gait, with an increased risk (and fear) of falling. They are likely to have a poor appetite and to have undergone a recent, unintentional loss of weight. Frail individuals are more likely than the nonfrail to experience impaired cognition and depression. They die sooner. Frailty, of course, is frequently complicated by a variety of coexistent illnesses. Among the biological correlates of frailty are sarcopenia (now readily measurable by dual-energy x-ray absorptiometry [DXA]), osteopenia (with an increased susceptibility to fracture), and activation of the inflammatory and coagulation systems, with a rise in inflammatory cytokines and several markers of coagulopathy. Age-dependent changes in a number of hormones also appear to promote the development of frailty in the elderly, particularly via their effects on muscle mass and strength, bone density, and by contributing to activation of the catabolic cytokines. In particular, serum levels of growth hormone (GH) and insulin-like growth factor-1 (IGF-1) decline progressively during aging, and an association between reduction in the levels of these hormones and the involution of advancing age has been proposed. It is not yet known whether, in comparison with their nonfrail counterparts, frail individuals consistently manifest larger reductions in GH and IGF-1 (and other anabolic hormones). More research is needed before it will be known whether the benefits of administering GH to the frail elderly will outweigh the disadvantages. The poor appetite and weight loss that occur in many frail individuals are likely to be accompanied by a degree of visceral protein depletion (with its attendant morbidity), which can be estimated by making serial measurements of indicators of visceral protein status such as transthyretin (TTR), retinol-binding protein (RBP), and albumin. One characteristic of the frailty syndrome that distinguishes it from the effects of aging per se is the potential reversibility of many of its features. Progressive resistance training is feasible for many elderly individuals-even the oldest old-and, by increasing muscle mass and strength, can ameliorate or reverse important aspects of physical frailty. To the extent that visceral protein depletion has been caused by an inadequate intake of calories and protein, consumption of a more adequate diet can result in betterment of the frail patient's nutritional status, as determined by clinical improvement and favorable changes in TTR, RBP, and albumin.

Aged↗

PubMed2003

Conceptualizations of frailty in relation to older adults.

AIM: The aim of this article is to discuss the concept of frailty and its adequacy in identifying and describing older adults as frail. BACKGROUND: Despite the dramatic increase in use of the term 'frailty' over the past two decades, there is a lack of consensus in the literature about its meaning and use, and no clear conceptual guidelines for identifying and describing older adults as frail. Differences in theoretical perspectives will influence policy decisions regarding eligibility for, and allocation of, scarce health care resources among older adults. METHOD: The article presents a literature review and synthesis of definitions and conceptual models of frailty in relation to older adults. The first part of the paper is a summary of the synonyms, antonyms and definitions of the term frailty. The second part is a critical evaluation of conceptual models of frailty. Six conceptual models are analysed on the basis of four main categories of assumptions about: (1) the nature of scientific knowledge; (2) the level of analysis; (3) the ageing process; (4) the stability of frailty. The implications of these are discussed in relation to clinical practice, policy and research. CONCLUSION: The review gives guidelines for a new theoretical approach to the concept of frailty in older adults: (1) it must be a multidimensional concept that considers the complex interplay of physical, psychological, social and environmental factors; (2) the concept must not be age-related, suggesting a negative and stereotypical view of ageing; (3) the concept must take into account an individual's context and incorporate subjective perceptions; (4) the concept must take into account the contribution of both individual and environmental factors.

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PubMed2004

The presence of frailty in elderly persons with chronic renal insufficiency.

BACKGROUND: Frailty has been defined as a tool to define individuals who lack functional reserve and are at risk for functional decline. We hypothesized that chronic renal insufficiency (CRI) would be associated with a greater prevalence of frailty and disability in the elderly. METHODS: This cross-sectional analysis used baseline data collected from the Cardiovascular Health Study, which enrolled 5,888 community-dwelling adults aged 65 years or older from 4 clinical centers in the United States. Renal insufficiency is defined as a serum creatinine level of 1.3 mg/dL or greater (> or =115 micromol/L) in women and 1.5 mg/dL or greater (> or =133 micromol/L) in men. Frailty is defined by the presence of 3 of the following abnormalities: unintentional weight loss, self-reported exhaustion, measured weakness, slow walking speed, and low physical activity. Disability is defined as any self-reported difficulty with activities of daily living. RESULTS: Among 5,808 participants with creatinine levels measured at entry, 15.9% of men (n = 394) and 7.6% of women (n = 254) had CRI. Prevalences of frailty (15% versus 6%; P < 0.001) and disability (12% versus 7%; P = 0.001) were greater in participants with CRI compared with those with normal renal function. After multivariate adjustment for comorbidity, CRI remained significantly associated with frailty (odds ratio, 1.76; 95% confidence interval, 1.28 to 2.41), but not disability (odds ratio, 1.26; 95% confidence interval, 0.94 to 1.69). CONCLUSION: Elderly persons with CRI have a high prevalence of frailty, which may signal their risk for progression to adverse health outcomes. If confirmed in other studies, identification of frailty in patients with CRI may warrant special interventions to preserve their independence, quality of life, and survival.

Activities of Daily Living↗

PubMed2003

Is grip strength a useful single marker of frailty?

BACKGROUND: chronological age is widely used as a marker of frailty in clinical practice. However there can be wide variation in frailty between individuals of a similar age. Grip strength is a powerful predictor of disability, morbidity and mortality which has been used in a number of frailty scores but not as a single marker of frailty. OBJECTIVE: to investigate the potential of grip strength as a single marker of frailty in older people of similar chronological age. DESIGN: cross-sectional study with prospective collection of mortality data. SETTING: North Hertfordshire, UK. SUBJECTS: 717 men and women, aged 64-74, born and still living in North Hertfordshire, who took part in a previous study to investigate the relationship between size at birth and ageing processes in later life. METHODS: the number of significant associations between grip strength and the ageing markers was compared with numbers between chronological age and the ageing markers. RESULTS: in men, lower grip strength correlated significantly with ten ageing markers compared to chronological age which was significantly associated with seven. In women, there were six significant relationships for grip compared to three for age. The greater number of relationships between grip strength and ageing markers was not explained by the association between grip strength and age, and remained after adjustment for adult size. CONCLUSIONS: grip strength was associated with more markers of frailty than chronological age within the narrow age range studied. Grip strength may prove a more useful single marker of frailty for older people of similar age than chronological age alone. Its validity in a clinical setting needs to be tested.

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PubMed2004

The estimation of relative fitness and frailty in community-dwelling older adults using self-report data.

BACKGROUND: While on average health declines with age, it also becomes more variable with age. As a consequence of this marked variability, it becomes more important as people age to have a means of summarizing health status, but how precisely to do so remains controversial. We developed one measure of health status, personal biological age, from a frailty index. The index itself is a count of deficits derived, in the first instance, from a clinical database. In our earlier investigations, personal biological age demonstrated a strong relationship with 6-year survival. Here we extend this approach to self-reported data. METHODS: This is a secondary analysis of community-dwelling people aged 65 years and older (n = 9008) in the Canadian Study of Health and Aging. The frailty index was calculated from 40 self-reported variables, representing symptoms, attitudes, illnesses, and function. Personal biological age was estimated for each individual as the age corresponding to the mean chronological age for the index value. Individual frailty (and the related construct of fitness) was calculated as the difference between chronological and personal biological age. RESULTS: The frailty index showed, on average, an exponential increase with age at an average rate of 3% per year. Although women, on average, demonstrate more frailty than men of the same chronological age, their survival chances are greater. The frailty index strongly correlated (Pearson r =.992 for women and.955 for men) with survival. CONCLUSIONS: A frailty index, based on self-report data, can be used as a tool for capturing heterogeneity in the health status of older adults.

Aged↗

PubMed2005

Frailty index as a measure of biological age in a Chinese population.

BACKGROUND: The concept of a frailty index, developed in Canadian elderly populations as an indicator of biological age as opposed to chronological age, was tested in an elderly Chinese population to determine whether it is applicable in a different ethnic and cultural setting. METHODS: A data set including 62 physical, psychological, and socioeconomic variables from a cohort of 2,032 persons 70 years and older (999 men, 1,033 women) was used. The distribution of the index was evaluated using the Cramer-von Mises goodness-of-fit test, and multiple linear regression was used to assess its relationship with age and sex. A biological age for each participant was calculated based on an inverse regression of age on mean frailty index and sex. The Cox proportional hazards regression model was used to assess the ability of biological age to predict death. RESULTS: The distribution of the frailty index most closely resembled a Weibull distribution. The frailty index increased with age until the mid-80s, when it leveled off, and was higher in women than men for each age group. The distribution of biological age is wider than that for chronological age, and it strongly predicted death. Women had an estimated 20% lesser chance of dying at a given time than did men of the same chronological age and degree of frailty. CONCLUSIONS: The study confirms the robustness of the concept and method of calculating the frailty index developed in elderly Canadian populations. It also suggests that the sex difference in life expectancy may have an underlying genetic basis independent of frailty.

Activities of Daily Living↗

PubMed2006

Factors contributing to frailty: literature review.

AIM: This paper presents a review of theoretical and research literature in order to identify the factors contributing to frailty. BACKGROUND: Frailty is a multifaceted gerontological concept that lacks a clear definition, but may result from an identifiable homogeneous cluster of bio-psycho-social-spiritual factors. METHOD: A total of 134 articles were identified through a search of the MEDLINE (1966 to July 2004), CINAHL (1982 to July 2004), PsychInfo (1985 to July 2004) and Ageline (1995 to July 2004) databases. Each article was reviewed to determine its fit with inclusion/exclusion criteria. Seven research and 11 theoretical articles were retained and further reviewed for methodological quality using a validity tool. FINDINGS: Seventeen different definitions of frailty were identified. Regardless of the differing definitions, common contributing factors could be identified. Physical, cognitive/psychological, nutritional and social factors, as well as ageing and disease, were evident in both the theoretical and research literature. CONCLUSIONS: Although there is strong agreement that a relationship exists between a cluster of factors and frailty, designation of the factors as contributors or outcomes of frailty differs. Without a clear explanatory theory of the path from contributors to frailty to outcomes, research will continue to produce confusing results. A theoretical framework that includes bio-psycho-social-spiritual factors as contributors to frailty is recommended as the most useful framework for gerontological nursing.

Age Factors↗

PubMed2006

Identifying frailty in hospitalized older adults with significant coronary artery disease.

OBJECTIVES: To characterize physiological variation in hospitalized older adults with severe coronary artery disease (CAD) and evaluate the prevalence of frailty in this sample, to determine whether single-item performance measures are good indicators of multidimensional frailty, and to estimate the association between frailty and 6-month mortality. DESIGN: Observational cohort study. SETTING: Inpatient hospital cardiology ward. PARTICIPANTS: Three hundred nine consecutive inpatients aged 70 and older admitted to a cardiology service (n = 309; 70% male, 84% white) with minimum two-vessel CAD determined using cardiac catheterization. MEASUREMENTS: Two standard frailty phenotypes (Composite A and Composite B), usual gait speed, grip strength, chair stands, cardiology clinical variables, and 6-month mortality. RESULTS: Prevalence of frailty was 27% for Composite A versus 63% for Composite B. Utility of single-item measures for identifying frailty was greatest for gait speed (receiver operating characteristic curve c statistic = 0.89 for Composite A, 0.70 for Composite B) followed by chair-stands (c = 0.83, 0.66) and grip strength (c = 0.78, 0.57). After adjustment, composite scores and single-item measures were individually associated with higher mortality at 6 months. Slow gait speed (< or =0.65 m/s) and poor grip strength (< or =25 kg) were stronger predictors of 6-month mortality than either composite score (gait speed odds ratio (OR)=3.8, 95% confidence interval (CI) = 1.1-13.1; grip strength OR = 2.7, 95% CI = 0.7-10.0; Composite A OR = 1.9, 95% CI = 0.60-6.1; chair-stand OR = 1.5, 95% CI = 0.5-5.1; Composite B OR = 1.3, 95% CI = 0.3-5.2). CONCLUSION: Gait speed frailty was the strongest predictor of mortality in a population with CAD and may add to traditional risk assessments when predicting outcomes in this population.

Aged↗

PubMedDate not supplied

Social determinants of frailty.

BACKGROUND: Frailty represents a body-wide set of a linked deterioration that occurs with ageing, but is susceptible to active intervention and is reversible. The concept of frailty should include broader environmental factors. A quantitative measure of frailty, the frailty index (FI), developed for elderly Canadians and shown to be valid for an elderly Chinese population, was examined for its association with socioeconomic, lifestyle, and social support network factors in an elderly Chinese cohort. OBJECTIVE: 2,032 people aged 70 years and over recruited by stratified random sampling of the population were surveyed in 1990-1991, and information obtained regarding physical and functional health, psychological factors, lifestyle, socioeconomic and social support factors. The FI was constructed from 62 variables covering cognitive, psychological and physical health, and tested for association with socioeconomic, lifestyle and social support factors using ANOVA and t test. RESULTS: The mean FI for women was higher than for men (0.16 +/- 0.08, n = 1,033 vs. 0.13 +/- 0.08, n = 999, p < 0.001, t test). For men, increasing frailty was observed with non-white collar occupations, inadequate expenses, no or little exercise, abstinence from alcohol, few relatives or neighbours and no or infrequent participation in helping others. For women, little contact with relatives (rather than number of relatives), and absence of participation in community/religious activities were additional factors. CONCLUSION: FI is influenced by social and environmental factors in keeping with the concept of frailty being multi-dimensional. Such a quantitative measure may be a useful indicator of the health of elderly populations as well as for public health measures to combat frailty.

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PubMed1994

Generalizations and applications of frailty models for survival and event data.

A variety of survival models with both discrete and continuously distributed frailty is considered within a framework that involves the specification of three sub-models. An intensity sub-model specifies how the intensity is related to values of covariates and frailty; a measurement sub-model specifies how fallible measures of frailty are related to it; and an exposure sub-model specifies how frailty is distributed within the population. The models include those in which frailty is due to omitted covariates and those where it represents a covariate that has been measured subject to error. Multivariate frailty is also considered, with particular emphasis on models suitable for application to genetically related individuals, notably twins. A numerical example illustrates the use of a model with multivariate frailty for data on repeated exercise times.

Angina Pectoris↗