Who are the frail elderly?

To even the most casual observer, the elderly are a very heterogeneous population. Some individuals remain fit and active into their ninth or tenth decades, whilst others show evidence of infirmity during their early sixties in the absence of an acute physical illness. This dissociation of biological and chronological age represents a continuum bounded by, in the parlance of contemporary gerontology, the terms 'fit' and 'frail' [1]. The lack of an agreed operational definition, however, has resulted in conflict and confusion in the gerontological literature. We propose a definition which, we believe, describes these extremes.