[Frailty, an enigmatic and controversial concept in geriatrics. The biological perspective].

Frailty is a controversial, complex and enigmatic concept. Because the world's population is aging, it has been possible to assess the impact of frailty over patients themselves as well as on their relatives, community and mainly on their caregivers. Health care personnel must be able to identify and understand this entity and its components. In addition during the 80's frailty was understood as synonymous with disability, chronic illness, or extreme aging; this perspective must be modified. The literature on frailty has increased exponentially in the last years. However, there is still not a well defined and universally recognized description or definition. The purpose of this review was to understand frailty and its consequences based on the most recent advances in the field of aging. Frialty is a multifactorial phenomenon and for purposes of this review, only biological characteristics are discussed.