A comparison of four frailty models

Frailty is a condition that places older persons at risk of poor outcomes when exposed to stressful events.1 Frailty is present in approximately 5% of the population aged 60 and older.2 Numerous studies have suggested that frailty is a predictor of functional deterioration and mortality.3–5 Models of frailty have been developed using three different domains: functional, deficit accumulation, and biological.6–11 The Frailty Index (FI) was developed based on the concept that deficit accumulation—a combination of symptoms, diseases, conditions, and disability—can predict frailty.9 A biological model of frailty based on five components—weight loss, exhaustion, low energy expenditure, slowness, and weakness—is known as the Cardiovascular Health Study (CHS) scale.12 The Study of Osteoporotic Fractures (SOF) scale included one functional and two biological factors in its frailty index—inability to rise from a chair five times without using the arms, weight loss, and reduced energy level.13 The CHS and FI measures are not practical for use in a busy clinic. The CHS scale requires measured performance (walking speed, grip strength) and is scored based on relative values in a population. The FI includes numerous items, typically 40 or more, and may include measured performance (e.g., cognition, physical performance). The SOF scale is brief and easy to administer in a clinic but requires measured performance (chair stands). The FRAIL scale was recently developed as a simple measure that combines components of functional, deficit accumulation, and biological frailty models.14,15 The FRAIL scale was constructed to include only interview questions and require minimal administration time so that physicians and other health professionals can easily use it in clinical practice. Initial studies have shown that the FRAIL scale predicts adverse health outcomes,16–18 but research directly comparing different models of frailty is limited,19,20 and these studies have not included the FRAIL scale. African Americans have a higher level of functional impairment and disability than do Caucasians21 and have been shown to have a higher prevalence of frailty than Caucasians using the CHS model.22 Thus there is a need for a brief frailty tool that can be used to identify African Americans at risk of disability and mortality so that early interventions can be developed. African American Health (AAH) is a population-based study of late middle-aged African Americans from two socioeconomically diverse areas of St. Louis. The AAH population has been demonstrated to have excess disability21 and represents a population that could benefit greatly from early frailty identification by clinicians. The objective of this study was to investigate how well the interview-based, clinic-friendly FRAIL scale predicts future disability and mortality compared with the clinic-friendly SOF scale, the phenotype-based CHS scale, and the comprehensive FI in the AAH cohort. It was hypothesized that the FRAIL, CHS, and SOF measures and the FI would have predictive validity for disability and mortality and that the predictive validity of the FRAIL scale for disability and mortality would be similar to that of the SOF and CHS scales and the FI using receiver operating characteristic (ROC) contrasts.