EDITORIAL

Now that we have a definition for physical frailty, what shape should frailty medicine take? Concepts of frailty sit at the heart of much current discourse about how we deliver and develop services for vulnerable older people. Yet the word frail is used variably and impre-cisely. Some of this might be attributable to the differences between lay and technical definitions, but there has also been a failure within the scientific literature to agree a core specifi-cation of ‘what is frail’. Two main theoretical constructs have come to dominate the conversation. Fried et al.’s phenotypic model defined a constellation of five possible components (weight loss, exhaustion, weakness, slowness and reduced physical activity), which indicate an underlying physiological state of multisystem dysregulation [1]. Rockwood and Mitnitski, meanwhile, described an accumulation of deficits model