People with frailty often have a number of very typical physical characteristics of frailty (known in research terms as the ‘frailty phenotype’).

These are:

  • weight loss
  • fatigue
  • weakness
  • slow walking speed
  • reduced physical activity

The physical health changes associated with frailty can also be illustrated in a visual scale, which gives us a quick and easy way to recognise different stages of frailty.  This example is taken from the Clinical Frailty Scale.


The phenotype model of frailty was first proposed by Linda P. Fried (an American geriatrician and epidemiologist) in order to characterise and present a standardised definition for the clinical syndrome of frailty. This model defined frailty as a clinical syndrome in which three or more of the following five criteria were present:

  1. Unintentional weight loss – the exact definition of amount of weight lost and over what period varies between studies but “10lb (c. 5kg) or more in past year” is often used.
  2. Fatigue or exhaustion – a self-reported measure with a positive response to a question covering how the person felt in the last month such as: “Did you feel that everything you did was an effort?”, “Did you feel exhausted without any reason?
  3. Weakness – measured through grip strength with the level defined by gender and body mass index.
  4. Slow walking (gait) speedtime to walk 4m adjusted for gender and standing height
  5. Low physical activity – based on self-reported levels of physical activity

A common feature across most of these criteria is loss of muscle mass, strength and functioning which is known as sarcopenia.

Fried found that this frailty phenotype had an overall prevalence of about 7% in community dwelling adults over the age of 65 years and was found to be independently predictive of adverse outcomes such as falls, disability, hospitalisation and death.

This model gives rise to a number of tools for identifying and assessing frailty.

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Go to: Tools for identifying and assessing frailty