A commonly cited definition is by Fried:
"a clinical syndrome in which three or more of the following criteria were present: unintentional weight loss (10 lbs in past year), self-reported exhaustion, weakness (grip strength), slow walking speed, and low physical activity" [4]A good clinical pointer is the 'get up and go' test which is often used in geriatric ward rounds to assess a person's mobility and the presence of difficulties that may not be apparent in the history and examination.
1. Santos-Eggimann B, Cuénoud P, Spagnoli J, Junod J. Prevalence of frailty in middle-aged and older community-dwelling Europeans living in 10 countries. J. Gerontol. A Biol. Sci. Med. Sci. 2009;64(6):675-681. Available at: http://www.ncbi.nlm.nih.gov/pubmed/19276189 [Accessed March 30, 2011].
2. Abellan van Kan G, Rolland Y, Houles M, et al. The assessment of frailty in older adults. Clin. Geriatr. Med. 2010;26(2):275-286. Available at: http://www.ncbi.nlm.nih.gov/pubmed/20497846 [Accessed March 30, 2011].
3. Xue Q. The frailty syndrome: definition and natural history. Clin. Geriatr. Med. 2011;27(1):1-15. Available at: http://www.ncbi.nlm.nih.gov/pubmed/21093718 [Accessed March 30, 2011].
4. Fried LP, Tangen CM, Walston J, et al. Frailty in older adults: evidence for a phenotype. J. Gerontol. A Biol. Sci. Med. Sci. 2001;56(3):M146-156. Available at: http://www.ncbi.nlm.nih.gov/pubmed/11253156 [Accessed March 30, 2011].