Differential Association of Frailty and Sarcopenia With Mortality and Disability: Insight Supporting Clinical Subtypes of Frailty

Objectives Sarcopenia and frailty have been shown separately to predict disability and death in old age. Our aim was to determine if sarcopenia may modify the prognosis of frailty regarding both mortality and disability, raising the existence of clinical subtypes of frailty depending on the presence of sarcopenia. Design A Spanish longitudinal population-based study. Setting and Participants The population consists of 1531 participants (>65 years of age) from the Toledo Study of Health Aging. Methods Sarcopenia and frailty were assessed following Foundation for the National Institutes of Health criteria and the Fried Frailty Phenotype, respectively. Mortality was assessed using the National Death Index. Functional status was determined using Katz index. We ran multivariate logistics and proportional hazards models adjusting for age, sex, baseline function, and comorbidities. Results Mean age was 75.4 years (SD 5.9). Overall, 70 participants were frail (4.6%), 565 prefrail (36.9%), and 435 sarcopenic (28.4%). Mean follow-up was 5.5 and 3.0 years for death and worsening function, respectively. Furthermore, 184 participants died (12%) and 324 worsened their functioning (24.8%). Frailty and prefrailty were associated with mortality and remained significant after adjustment by sarcopenia [hazard risk (HR) 3.09, 95% confidence interval (CI) 1.84-5.18; P < .001; HR 1.58, 95% CI 1.12-2.24, P = .01]. However, the association of sarcopenia with mortality was reduced and became nonsignificant (HR 1.43, 95% CI 0.99-2.07, P = .057) when both frailty and sarcopenia were included in the same model. In the disability model, frailty and sarcopenia showed a statistically significant interaction (P = .016): both had to be present to predict worsening of disability. Conclusions and Implications Sarcopenia plays a relevant role in the increased risk of functional impairment associated to frailty, but that seems not to be the case with mortality. This finding raises the need of assessing sarcopenia as a cornerstone of the clinical work after diagnosing frailty.