Frailty: different tools for different purposes?

Abstract

In this issue, Ravaglia et al. [ 1 ], report on ‘a frailty score’, which they have tested as a predictor of a range of adverse health outcomes which they characterise as ‘frailty outcomes’ in people aged 65+ years (mean age at baseline was 74.7) [ 1 ]. The outcomes were death (14.6% of the baseline sample), fractures, hospitalisation, and new onset or worsening of capacity to perform activities of daily living (ADL) during the next 4 years. Their model was arrived at through statistical exploration of data from a longitudinal population study of 1,016 individuals in Italy. The nine variables emerging after multivariate analysis were age >80 years, male gender, low physical activity, co-morbidity, sensory deficits, calf circumference <31 cm (taken as an indicator of sarcopenia), dependence in Instrumental ADL, a Tinetti gait and balance performance score ≤24, and pessimism about one's health compared to others. Together they produce a numerical score which at various cut-points tested was significantly predictive of the ‘frailty outcomes’. While acknowledging that their prognostic score is not yet adequately developed and requires at least to be tested in a remote cohort of older people, the authors suggest that their findings support further investigation of frailty scores for use in clinical geriatric practice. Consideration of the frailty concept and its utility for the geriatrician is certainly welcome. Indeed, in this journal, Rockwood challenged the clinical geriatrics community to recognise frailty as the central raison d'etre of the specialty [ 2 ] and went on to discuss the theoretical and empirical work needed to make a definition of frailty valid and useful [ 3 ]. Part of the work needed is to consider what frailty means from a range of perspectives. Within the clinical research community, particularly in the United States, considerable effort has been made in recent years to achieve a consensus [ 4 , 5 ] and during 2005–06, the Journal of the American Geriatrics Society published 14 papers with frailty in the title. Further progress was reported from the Second International Working Meeting on Frailty and Aging held in Montreal in 2006, leading to several fascinating papers, setting out a spectrum of approaches, published in July 2007 in a special section of the Journals of Gerontology [ 6–9 ]. The shared central notion about frailty is of an older person who is at heightened vulnerability to adverse health status change. The phenotype fitting this has been operationalised with five components—unintentional weight loss, self-reported fatigue and diminished physical activity, and measured impairment (comparative to age-standardised norms) of grip strength and gait speed [ 10 ]. Although this omits cognitive and psychosocial features which are well known to be predictive of adverse health outcomes such as loss of functional ability, institutionalisation and death, this physical frailty phenotype has demonstrated predictive power for adverse health outcomes in several cohorts of older people [ 10 , 11 ]. This highlights two of the contesting concepts about frailty. The first concept is of a syndrome associated with underlying physiological and metabolic changes, which may be inter-related and which are responsible for driving progressive physical and cognitive impairments through to loss of functional capacity, often helped on the way by acute or chronic disease or injury. This approach was encapsulated in a definition of frailty proposed in this journal a decade ago—‘a condition or syndrome which results from a multi-system reduction in reserve capacity to the extent that a number of physiological systems are close to, or past, the threshold of symptomatic failure. As a result, the frail person is at increased risk of disability or death from minor external stresses’ [ 12 ]. This emphasises the pathophysiological causal pathway. Subsequent work has thrown up a number of candidates to occupy this pathway, such as cytokines and other components of the inflammatory response [ 13–15 ]. An alternative approach has been to treat frailty as a collective of risk factors for future adverse events, while not necessarily bearing any pathophysiological relationship to these outcomes. This more pragmatic approach is about identifying people at higher risk of pre-defined adverse outcomes. This could be done for a range of purposes and in a range of contexts and these considerations will influence the measures which are suitable, the thresholds for defining high risk (and therefore by implication frailty) and the time interval between the measurement and the outcome. Only the most general concept of frailty could retain this flexibility. The first approach, of a pathophysiologically driven syndrome, is supported by evidence that differentiates it from ageing. Whether frailty changes are inevitable, as long as premature death does not intervene, remains uncertain [ 9 ] but it seems that frailty is also more than j