Revisiting the hypothesis of syndromic frailty: a cross-sectional study of the structural validity of the frailty phenotype.

BACKGROUND: Fried's Phenotype Model of Frailty (PMF) postulates that frailty is a syndrome. Features of a syndrome are a heterogeneous population that can be split into at least two classes, those presenting and those not presenting the syndrome. Syndromes are characterized by a specific mixture of signs and symptoms which increase in prevalence, from less to more severe classes. So far, the null hypothesis of homogeneity - signs and symptoms of frailty cannot identify at least two classes - has been tested using Latent Class Analysis (LCA) on the five dichotomized components of PMF (unintentional weight loss, exhaustion, weakness, slowness, and low physical activity). The aim of this study is to investigate further the construct validity of frailty as a syndrome using the extension offered by Factor Mixture Models (FMM). METHODS: LCA on dichotomized scores and FMM on continuous scores were conducted to test homogeneity on the five PMF components in a sample of 1643 community-dwelling older adults living in Québec, Canada (FRéLE). RESULTS: With dichotomized LCA, three frailty classes were found: robust, prefrail and frail, and the hypothesis of homogeneity was rejected. However, in FMM, frailty was better represented as a continuous variable than as latent heterogeneous classes. Thus, the PMF measurement model of frailty did not meet the features of a syndrome in this study. CONCLUSION: Using the FRéLE cohort, the PMF measurement model validity is questioned. Valid measurement of a syndrome depends on an understanding of its etiological factors and pathophysiological processes, and on a modelling of how the measured components are linked to these processes. Without these features, assessing frailty in a clinical setting may not improve patient health. Research on frailty should address these issues before promoting its use in clinical settings.

Are frailty components associated with disability in specific activities of daily living in community-dwelling older adults? A multicenter Canadian study.

Current studies show the relevance of geriatric prevention and rehabilitation programs to slow down the development of disability in community-dwelling older adults who are becoming frail. This evidence reveals the importance of improving knowledge on how individual components of frailty and specific disability in basic and instrumental activities of daily living (ADL) are related, to offer early, targeted, and tailored interventions. The objective was to examine the association between each of the five frailty phenotype components (weakness, slowness, exhaustion, low physical activity, weight loss) and disability in specific ADL pertaining to physical aspects (bathing, dressing, cutting toe nails, transportation, shopping, housekeeping, food purchasing, food preparation) and cognitive aspects (finances, telephone, medication). A cross-sectional design involving 1643 community-dwelling older adults (65+) from the longitudinal multi-center FRéLE study was used. Disability was defined as needing help or being unable to perform specific ADL. Multiple logistic regressions were adjusted for socio-demographic characteristics, clinical variables, and for 4 other frailty components. Results showed that low physical activity and slowness were significantly linked to disability in all physical and cognitive aspects of ADL (OR: 1.71-9.42; p<0.05), except using the telephone. Notably, all frailty components except weight loss were associated with disability in the physical aspects of instrumental ADL (transportation, shopping, housekeeping, food purchasing, food preparation) (OR: 1.73-9.42; p<0.05). This study helped identify the relevant frailty components as targets in community-based prevention and rehabilitation programs. Easily imbedded interventions in daily routines should be promoted earlier in the frailty process to delay or reduce disability.