Introduction to Frailty

Introduction[edit | edit source]


Frailty is a clinical state that is associated with an increased risk of falls, harm events, institutionalisation, care needs and disability/death.[1]

  • It affects quality of life
  • Becoming more common with ageing populations.[1]
  • Estimated that 25% to 50% of individuals aged over 85 years are frail.[2]

While it is generally accepted that frailty exists, it remains difficult to define as it manifests differently in each individual. A working definition of frailty is as follows:

  • it is a distinct clinical entity from ageing, but it is related to the ageing process. It consists of multi-system dysregulation leading to a loss of physiological reserve. This loss of reserve means that the individual living with frailty is in a state of increased vulnerability to stressors meaning they are more likely to suffer adverse effects from treatments, diseases or infections.
  • Morley et al (2013) also provide the following definition:

“Frailty is a clinical state in which there is an increase in an individual’s vulnerability for developing increased dependency and/or mortality when exposed to a stressor.”[3]

Thus, there are two key concepts that can be taken from these definitions:[1]

  1. Frailty is separate from, but related to ageing. While older people tend to be more frail, you will not be frail just because you are old. Frailty depends on your physiological state and how well you can respond to stressors (injury/illness).[1]
  2. Frailty involves multiple systems rather than just a single body system. Frail individuals will usually have a number of co-morbidities (eg cardiovascular, musculoskeletal and neurological).[1]

Frailty is a dynamic state - there is evidence that frailty can be modifiable and that it can be reversed more easily than disability.[4] This is significant as it means that an individual's frailty level can be influenced by our interventions.[1]

Overall, if unmanaged, a frail individual will follow a trajectory towards disability and death.[1][4]

Models of Frailty[edit | edit source]


There are two main theories that underpin the concept of frailty:

  1. Fried's Phenotype Model
  2. Rockwood's Accumulation of Deficits Model.

It is important to understand that these are not competing models. They should be considered as complementary - both have been validated and have been used to develop various assessment tools and treatment indicators.

Fried's Phenotype Model[edit | edit source]

Fried's Phenotype Model was first published in 2001.[5] It is a yes-no model based on five subcategories. Each subcategory is scored as 0 (no) or 1 (yes). It assumes an individual is frail if s/he has a score of greater than three.[1] The five categories are:

  1. Physical Inactivity
  2. Low muscle strength - can be measured in grip strength - <21 kgf in men and <14 kg in women (NB this is dependent on ethnicity)
  3. Slow gait speed - less than 0.8 m/s with or without a walking aid
  4. Exhaustion/ fatigue - this is self-reported
  5. Weight loss - loss of 10 lbs/4.5 kg or more in 1 year

The scoring is as follows:

  • 0-1 = not frail
  • 1-2 = pre-frail
  • 3+ = frail (mild, moderate and severe)

When using this model, it is important to remember that frailty is a multi-system dysregulation.

  • If an impairment is clearly due to a mono-articular or single system problem (eg low grip strength following a hand injury) then this must be considered when assessing for frailty.
  • Note also that this model focuses solely on physical attributes of frailty.
  • Some researchers, therefore, consider that it is an incomplete model as it does not address cognitive aspects or chronic conditions which are associated with frailty.[6] However, this focus on physical attributes makes Fried's Model useful for physiotherapists as it provides clear direction when creating treatment plans to address frailty eg. if a patient is shown to have low muscle strength, treatment would focus on strengthening; patients who are found to be physically inactive would need to increase their activity levels.[1]

Rockwood's Accumulation of Deficits Model[edit | edit source]

The Rockwood Model considers how frailty can be the result of an accumulation of a number of deficits.[7] This model shows that as people age, they develop health deficits.

  • Not all adults develop the same number of deficits. Thus, some become frail whereas others do not.[8]

This accumulation of deficits can be quantified using the Frailty Index.

  • In this index, 92 parameters of symptoms, signs, abnormal laboratory results, disease states and disabilities - ie deficits - were used to define frailty.[2]
  • The number of parameters has subsequently been reduced to around 30 variables.[2]
  • An individual's Frailty Index score indicates how many deficits are present - the more deficits, the greater the chance s/he is frail.[7]
  • The Frailty Index score is calculated by dividing the total number of impairments by the total number of parameters examined. An individual is considered more frail the closer their overall score is towards 1.0.

Several studies have found that the Frailty Index score is strongly related to the risk of death and institutionalisation.[2] It is, therefore, considered a useful model for primary care (GPs or Geriatricians), but given it can be time-consuming to complete, additional measures have been developed that are quicker to use including:

  • The electronic Frailty Index (eFI), which was developed by Clegg and colleagues in 2016.[9] It identifies frailty using data that is held on primary care databases. It categorises patients into four categories based on this data: fit older individuals, as well as individuals with mild frailty, moderate frailty and severe frailty.[9]
  • The Clinical Frailty Scale (see image below), is a straightforward and accessible tool that can be used to quickly and simply assess frailty. It has been validated in adults aged over 65 years.[10]
    • A score from 1 (very fit) to 9 (terminally ill) is given based on the descriptions and pictographs of activity and functional status.[11]
    • Particular attention should be paid to those who score 5 or more as this is the marker for requiring a comprehensive geriatric assessment and often referral to geriatric or frailty specialists,
    • A 2017 Cochrane review found that older people are more likely to be alive and in their own homes at follow-up if they received CGA on admission to hospital.[12]
Rockwood's Clinical Frailty Scale. 1-9 1 being not frail and 9 being terminally ill.

Summary[edit | edit source]

  • Frailty is a clinical state involving multiple systems that is related to ageing.
  • Frailty can ultimately lead to disability and death, but it is not a fixed state and can be positively affected if appropriate interventions are provided.
  • Two key models underpin the concept of frailty: Fried's Phenotype Model and Rockwood's Accumulation of Deficits Model. Fried’s Model focusses solely on the physical aspects of frailty whereas Rockwood's Model considers how health deficits accumulate, which increases the likelihood an individual will be frail.

References[edit | edit source]

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Buxton S. An Introduction to Frailty course. Physioplus. 2020.
  2. 2.0 2.1 2.2 2.3 Clegg A, Young J, Iliffe S, Rikkert MO, Rockwood K. Frailty in older people, The Lancet. 2013; 381(9868): 752-62. Available from
  3. Morley JE, Vellas B, Abellan van Kan G, Anker SD, Bauer JM, Bernabel R et al. Frailty consensus: a call to action. J Am Med Dir Assoc. 2013. 14(6): 392-7.
  4. 4.0 4.1 Clegg A, Bates C, Young J, Ryan R, Nichols L, Teale EA et al. Development and validation of an electronic frailty index using routine primary care electronic health record data. Age and Ageing. 2016; 45(3): 353–60,
  5. Fried LP, Tangen CM, Walston J, Newman AB, Hirsch C, Gottdiener J, Seeman T et al. Frailty in older adults: evidence for a phenotype. J Gerontol. 2001. 56A(3): 146-56.
  6. Fried LP, Xue QL, Cappola AR, Ferrucci L, Chanves P, Varadhan R, Guralnik JM, Leng SX, Semba RD, et al. Nonlinear multisystem physiological dysregulation associated with frailty in older women: implications for etiology and treatment. J Gerontol. 2009. 64(10): 1049-57.
  7. 7.0 7.1 Rockwood, K, Mitnitski A. Frailty in Relation to the Accumulation of Deficits. The Journals of Gerontology Series A Biological Sciences and Medical Sciences. 2007; 62(7): 722-7. Available from
  8. Rockwood K. Conceptual Models of Frailty: Accumulation of Deficits. Can J Cardiol. 2016;32(9):1046‐1050.
  9. 9.0 9.1 Lansbury LN, Roberts HC, Clift E, Herklots A, Robinson N, Sayer AA. Use of the electronic Frailty Index to identify vulnerable patients: a pilot study in primary care. British Journal of General Practice. 2017;  67 (664): e751-e756.
  10. Acute Frailty Network. Clinical Frailty Scale. Available from (accessed 12 June 2020).
  11. Juma S, Taabazuing MM, Montero-Odasso M. Clinical frailty scale in an acute medicine unit: a simple tool that predicts length of stay. Can Geriatr J. 2016; 19(2): 34-9. Available from:
  12. Ellis G, Gardner M, Tsiachristas A, Langhorne P, Burke O, Harwood RH, Conroy SP, Kircher T, Somme D, Saltvedt I, Wald H. Comprehensive geriatric assessment for older adults admitted to hospital. Cochrane database of systematic reviews. 2017(9). Available from: (last accessed 4.5.2019)