Intended for healthcare professionals

Clinical Review

Functional assessment in older people

BMJ 2011; 343 doi: (Published 22 August 2011) Cite this as: BMJ 2011;343:d4681

Re: Functional assessment in older people

Dear Sir

We read with interest the article entitled "Functional Assessment in older people". We feel a truly patient-centered approach requires re-framing current conceptual models to robustly manage multi-dimensionality, and better deal with high levels of complexity.

Frailty has been defined as a biological syndrome of accumulated deficit across multiple physiological systems, resulting in increased vulnerability to external stressors and increased risk of adverse outcomes. Though conceptually satisfying, this definition has been difficult to operationalize, hence absolute clinical or academic consensus has not been achieved. In general, two approaches have been adopted: a phenotypical model(1) and a frailty index(2). The former is based on predefined criteria derived from observable bio-physical phenomena, whilst the latter is a quantification of accumulated deficit.

Studies have confirmed the validity of these approaches in predicting health outcomes (e.g. mortality and institutionalisation) (1, 3). The phenotype model is concise, and has correlation with bio-markers associated with frailty. The index model is computationally feasible, reproducible over populations and provides the ability to stage frailty. Both approaches have recognised limitations. Early phenotype models typically exclude dimensions, for example cognition, which have subsequently been shown to be significant. The frailty index has significant data requirements that may limit clinical acceptability in specific environments, and does not capture the severity of each deficit effectively (4).

Three additional dimensions are not fully captured by the current definitions. Firstly, though associated with disability and vulnerability, frailty is often perceived be distinct. Disability is often defined as impairment that limits activity, resulting in restriction to participation in normal function. Vulnerability is often defined as the inability to withstand effects of external environmental stressors. These artificial distinctions result from different conceptual constructs that arguably view complexity from biological (frailty), social (vulnerability) and functional (disability) lenses. This may lead to fragmented approaches to healthcare, and inconsistent measurement of process and outcomes.

Secondly, the models do not effectively capture the dynamic nature of frailty over time. In clinical practice, frailty is observed to change qualitatively and quantitatively over time within individuals. Current statistical models of frailty comfortably fulfil the assumption of frailty variability between individuals, but do not capture intra-patient variability over time.

Thirdly, frailty is also often only connected with inevitable biological processes associated with the senescence of ageing. Recent evidence suggests that biological deficits and specific socio-environmental stressors accumulated early in childhood predict the development of the frailty phenotype(5). There are considerable arguments for a life-course approach(6). Age on its own is insufficient to determine an individual’s position on the frailty-fitness spectrum(7).

To meet these challenges, we propose a more integrated model(Fig.1), which we shall term fragility. We propose that a fragile person is one with accumulated and interacting deficits from 4 domains: physical, mental health and psychological, socio-economic and environmental domains. This results in a risk of harm beyond the effect of individual deficits or external stressors. Additionally, fragility is a dynamic condition that can occur at any point in life.

Adopting this new operational view of fragility will positively affect our approaches of care. Firstly, valid fragility assessment requires variables to be measured in all the above domains. Fragility assessments that focus only on some variables may miss significant deficits or stressors.

Secondly, we need robust assessment systems that have the ability to monitor fragility’s multidimensional characteristics qualitatively and quantitatively over time, as well as across health and social care sectors.

Thirdly, operational and statistical definitions must recognise three factors: the accumulation of deficits and external stressors; interactions between deficits, and with external stressors; and the severity of individual deficits and their impact on other domains.

Fourthly, actions taken before a person becomes fragile to prevent the accumulation of deficits could prevent, delay or reduce fragility later in the life-course.

Lastly, there are very well defined pathophysiological processes in the elderly (e.g. chronic inflammation-malnutrition; dysregulation of steroid hormones; sarcopaenia) which lead to a common endpoint of increased risk of harm. Exploration of other conditions with these processes in younger age groups (e.g. peripheral muscle wasting with COPD) may indicate patient groups who would benefit from generalisable knowledge of multidimensional assessment and intervention. More controversially, patient groups whose pathophysiology are not similar to those associated with increased age, but have similar levels of complexity (e.g. patients with cerebral palsy) may also benefit from being defined as fragile, with consequent transferable, if not generalisable learning.


The viewpoint of fragility has value in so far as it describes accurately a cohort of complex vulnerable patients who are at increased risk of adverse events, and suffer disproportionately the effects of fragmented health and social care. The proposed model provides a meeting point for an individual patient’s requirement and targetted interventions. As complexity increases, so must standardisation of care give way to customisation. Improving quality of life is just as important as extending quantity of life. Simple interventions accrue to reduce patient harm(Fig. 1). Good outcome is individual patient defined. It is highly specific to the individual’s preference, need and point of view. Professional knowledge and lay experience must work reciprocally and equally.

1. Fried LP, Tangen CM, Walston J, Newman AB, Hirsch C, Gottdiener J, et al. Frailty in older adults: evidence for a phenotype. Journals of Gerontology Series A Biological Sciences & Medical Sciences. 2001;56(3).
2. Rockwood K, Song X, MacKnight C, Bergman H, Hogan DB, McDowell I, et al. A global clinical measure of fitness and frailty in elderly people. Canadian Medical Association Journal. 2005;173(5):489.
3. Rockwood K, Howlett SE, MacKnight C, Beattie BL, Bergman H, Hebert R, et al. Prevalence, attributes, and outcomes of fitness and frailty in community-dwelling older adults: report from the Canadian study of health and aging. J Gerontol A Biol Sci Med Sci. 59. United States2004. p. 1310-7.
4. Wou F, Conroy S. The frailty syndrome. Medicine. 2013;41(1):13-5.
5. Alvarado BE, Zunzunegui MV, Beland F, Bamvita JM. Life course social and health conditions linked to frailty in Latin American older men and women. J Gerontol A Biol Sci Med Sci. 63. United States2008. p. 1399-406.
6. Kuh D. A life course approach to healthy aging, frailty, and capability. J Gerontol A Biol Sci Med Sci. 62. United States2007. p. 717-21.
7. Romero-Ortuno R, O'Shea D. Fitness and frailty: opposite ends of a challenging continuum! Will the end of age discrimination make frailty assessments an imperative? 2013.

Disclaimer: This article presents independent research commissioned by the National Institute for Health Research (NIHR) under the Collaborations for Leadership in Applied Health Research and Care (CLAHRC) programme for North West London. The views expressed in this publication are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health. JTY Soong Clinical Research Fellowship is supported by the Royal College of Physicians London

Competing interests: No competing interests

17 May 2013
John TY Soong
Acute Medicine Trainee
Andrew Bailey, Derek Bell
Imperial College London
NIHR CLAHRC NWL, Imperial College London, 369 Fulham Road SW10 9NH