ABSTRACT
Frailty has emerged again in the twenty-first century as an important concept for health and social care workers. Disease and disability of older people is the result of the complex and cumulative interactions between genes, ageing-related molecular damage and environmental factors. The emerging consensus is that, just as there is no biological master clock dictating lifespan, there is no single common pathway for frailty. Conversely, as would be predicted by the disposable soma theory, evolution has resulted in sufficient but not excessively wasteful redundancy across the many cellular and physiological processes vital to life. Accumulation of damage in the form of highly variable age-related changes and specific diseases comes together to form a critical mass, reducing the reserve across a complex system. Recognition, measurement and modification of this frailty are the business of the twenty-first century, just as the last century was the era of disease.
