Elsevier

Ageing Research Reviews

Volume 10, Issue 1, January 2011, Pages 104-114
Ageing Research Reviews

Review
Outcome instruments to measure frailty: A systematic review

https://doi.org/10.1016/j.arr.2010.09.001Get rights and content

Abstract

Frailty is one of the greatest challenges for healthcare professionals. The level of frailty depends on several interrelated factors and can change over time while different interventions seem to be able to influence the level of frailty. Therefore, an outcome instrument to measure frailty with sound clinimetric properties is needed. A systematic review on evaluative measures of frailty was performed in the databases PubMed, EMBASE, Cinahl and Cochrane. The results show numerous instruments that measure the level of frailty. This article gives a clear overview of the content of these frailty instruments and describes their clinimetric properties. Frailty instruments, however, are often developed as prognostic instruments and have also been validated as such. The clinimetric properties of these instruments as evaluative outcome measures are unclear.

Research highlights

▶ An outcome instrument with sound clinimetric properties to evaluate changes in frailty is needed. ▶ Frailty level is not equivalent to the sum of its’ components. ▶ Most frailty instruments do not include factors in multiple dimensions. ▶ For most frailty instruments only construct validity has been studied. ▶ The Frailty Index seems to be the most suitable instrument to evaluate effect of intervention. ▶ There is a need for more consistency and transparency in frailty research.

Introduction

Frailty is one of the greatest challenges for healthcare professionals in societies faced with ageing populations (Levers et al., 2006). It is associated with adverse health outcome, dependency, institutionalization and mortality (Fried et al., 2001, Fried et al., 2004). Since the population of (frail) elderly is still growing and health care utilization among this population is increasing, prevention of frailty or maintenance/reduction of the level of frailty should have priority among geriatric health care professionals. While frailty is known to be changeable over time (Hubbard et al., 2009a, Gill et al., 2010) it is, at this point, still unclear to what extent the level of frailty can be influenced by interventions. Therefore, an evaluative outcome instrument to measure frailty with sound clinimetric properties is needed (De Lepeleire et al., 2009). The aim of this systematic review is to find the best available frailty instrument that could be used as an evaluative outcome measure in clinical situations and observational and experimental studies.

The causes of frailty are not fully understood. A pathophysiological pathway that shows similarities with, but is not identical to the ageing process, is suggested. A chronic inflammation process, impaired immunity, neuroendocrine dysregulations and metabolic alterations seem to be related to frailty but true comprehension of the involved pathway is still lacking (Fulop et al., 2010). Even though the underlying mechanism of frailty is not fully understood, frailty is, since early publications, considered to be a physiologic loss of reserve capacity and resistance to stressors (Fried et al., 2001, Rockwood et al., 1994). As a result, environmental factors have more influence on the decline of wellbeing (Strawbridge et al., 1998). A remarkable finding in frailty is that not all frail elderly experience the same symptoms and that frailty can be present in the absence of specific diseases, but more likely in combination with or as a consequence of co-morbidity (Fried et al., 2004, Fulop et al., 2010). This means that frailty is not identical to co-morbidity. Because of similarities and inter relationships between the biological pathways of frailty, ageing and age related chronic disease, a definitive differentiation between these pathways is difficult to make (Fulop et al., 2010). Such an interacting process also applies to disability, one of the main consequences of frailty. Frail elderly with the same number of co-morbidities can suffer from very different levels of disability (Fried et al., 2004). The reason for this is that disability is also influenced by other than biological or physiological factors, for example personal characteristics including psychological state, emotional state and coping style. There is also an interaction with the physical and social environment, which can stimulate or hinder participation in activities.

Therefore, in the last few years, frailty is acknowledged to be not only a biological or physiological state, but also a multidimensional concept (Walston et al., 2006). There are multiple interrelated (risk) factors with great variety that can disrupt the physiological equilibrium of elderly. A complicating factor in understanding and defining frailty is that some (risk) factors that are involved in frailty can primary be seen as causes of the physiological process while other factors are merely consequences of the disturbed equilibrium which, however, also indirectly have an influence on the state of the physiological system (Fulop et al., 2010). This is obvious in the extent of disability: frailty causes disability, but when activity increases and disability decreases this slows down the frailty process (De Lepeleire et al., 2009). This means that there seems to be a dynamic system in which interrelated causes and consequences remain to be clarified.

Most authors consider examining risk factors associated with frailty, as an important item in prevention and curative care. However, the used definitions of frailty differ subtly and also the conceptualization of the multiple domains (Strawbridge, Rockwood, Fried, Jones, Mitnitski etc.). Recently, an integral conceptual model of frailty was presented that reflects current thinking on frailty and is based on the following definition of frailty: ‘Frailty is a dynamic state affecting an individual who experiences losses in one or more domains of human functioning (physical, psychological, and social), which is caused by the influence of a range of variables and which increases the risk of adverse outcomes’ (Gobbens et al., 2010a, p. 85). Because this definition reflects the changeability of frailty over time and emphasizes that the interacting factors in the physical, psychological and social domain are part of a complex dynamic system, we take this definition as a starting point.

Within each of the physical, psychological and social dimension various (risk) factors or determinants for frailty exist. The complex interaction between these factors determines and influences the level of frailty. The total level of frailty is therefore not equivalent to the sum of its components. The actual level (the state at a certain point of time) of frailty can be positioned on a continuum between frail and not frail (Gobbens et al., 2009). But this level of frailty can change over time in either direction, meaning that one can become more or less frail. Evidence suggests that there are opportunities to influence the level of frailty positively by means of interventions like hormone replacement, nutrition or physical activity (Hubbard et al., 2009a, De Lepeleire et al., 2009, Chin A Paw et al., 2008, Peterson et al., 2009). To explore the extent to which interventions can influence the level of frailty, an evaluative outcome measure on frailty is needed (De Lepeleire et al., 2009). Such an instrument should incorporate the multiple dimensions of frailty to reflect the complex interaction of multiple (risk) factors that, in this interaction, attribute to the total level of frailty and should be able to distinguish multiple levels of frailty and therefore be able to measure change.

Based on recent studies (Gobbens et al., 2009, Gobbens et al., 2010b, Gobbens et al., 2010c, Karunananthan et al., 2009, Sourial et al., 2009) and after ample discussion we composed a list of eight frailty (risk) factors that are mentioned to be of great importance to the concept of frailty. These factors include in the physical dimension: nutritional status, physical activity, mobility, strength and energy, in the psychological dimension: cognition and mood, and in the social dimension: lack of social contacts and social support (Markle-Reid and Browne, 2003, Gobbens et al., 2007).

Measuring the level of frailty is problematic for several reasons. Multiple theoretical and operational definitions have been suggested in the last decade. Numerous functional tests, questionnaires and indexes to categorize frailty are available and these instruments aim at highly different sub-populations of elderly people (Cigolle et al., 2009, Van Iersel and Rikkert, 2006, Hubbard et al., 2009b). The clinimetric properties of these instruments, such as validity, reliability and agreement, responsiveness and interpretability for general elderly populations are unclear. Furthermore, it is not generally known whether these instruments include one or more frailty dimensions or a multiple level scoring system to be sensitive enough to measure changes over time.

In conclusion, to use frailty as an outcome in clinical trials, a measurement instrument on frailty should be available that is multidimensional and captures the dynamic nature of this concept by means of a multiple level scoring system. Also, as applies to any measurement instrument, the instrument has to show sound clinimetric properties. The aim of this systematic review is to assess frailty instruments on clinimetric properties and to search for the best available frailty instrument that can be used as an evaluative outcome measure in clinical practice and that is useful in observational and experimental studies.

Section snippets

Literature search and inclusion

A broad systematic literature search was performed in the bibliographic databases PubMed, EMBASE, Cinahl and Cochrane. We used the following search terms to search for measurement instruments: ‘questionnaire’, ‘self-report’, ‘self-assessment’, ‘outcome measure’ and ‘outcome assessment’ in combination with ‘frail elderly’. The search was performed for articles published from the start date of the involved database until 23 February 2010. Potentially relevant articles were identified by reading

Literature search and inclusion

The literature search resulted in a total number of 2232 hits. In PubMed, 1270 articles were found, in EMBASE 464, in Cinahl 256 and 242 in Cochrane. After duplicate removal, 1600 articles were left. The first rater (NdV) included 28 studies from the database after scanning title and abstract on our predefined inclusion criteria, 17 articles were included by the second rater (JBS). There was initial agreement on 12 instruments between both raters. Another 8 instruments were added by discussing

Discussion

This review presents an overview of existing frailty instruments. Based on the results of this study we can conclude that many frailty instruments have been developed in recent years. We identified twenty instruments in current literature. To the author's knowledge this is the first time a systematic overview of all frailty instruments is given. This overview is a first step towards more transparency in frailty research and clinical practice. We assessed all the frailty instruments on eight

Conflict of interest statement

None declared.

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