Frailty and multimorbidity: Two related yet different concepts.

The extension of life expectancy is a global phenomenon. The growth in the ageing population has created a new health scenario in which there is a higher prevalence of frailty and multimorbidity. The attention received by both conditions derives from their strong association with disability, hospitalization, and death. The aim of the present paper is to conceptualize and differentiate these terms and to discuss their interrelations. We conclude that, yet related, they represent two different clinical conditions. Frailty identifies the increased vulnerability to stressors due to a dynamic, non-linear, and multidimensional depletion of physiological reserve and redundancy, whereas multimorbidity refers to the coexistence of two or more clinically manifest chronic diseases.