The evaluation of daily functioning as part of the operational definition of frailty: a systematic review

Background: The population is ageing, not all older adults are healthy and vital, a considerable part of them are frail. Disability in activities of daily living (ADL) can play multiple roles in frailty. Definitional confusion arises between frailty and disability due to the similarity of associated outcomes and the frequency of co-occurrence between the two. This systematic review aims to identify which frailty instruments incorporate ADL. Method: A systematic search was performed in PubMed, Web of Knowledge and PsycINFO with the terms (‘‘Aged’’[Mesh] OR ‘‘Frail Elderly’’[Mesh] OR ‘‘Aged, 80 and over’’[Mesh]) AND Frailty AND (‘‘Diagnosis’’[Mesh] OR ‘‘Risk Assessment’’[Mesh] OR ‘‘Classification’’[Mesh]). The identified instruments were analysed and categorised in basic- (b-), instrumental- (i-) and advanced- (a-) ADL. Results: In total 144 articles described 149 frailty instruments. Adistinction can be made between a physical (n = 47), multidomain (n = 98), comorbidity (n = 1), and biomarker model (n = 3). At least one ADL was present in 77.9% of the instruments: 71.1% concerned b-ADL, 55.3% i-ADL and 33.6% a-ADL. Not all included ADL have the same aim, e.g. measuring physical activity, weakness, slowness etc. If these were excluded, the results would decrease to 53.0%, 50.3, 36.2%, and 10.1% respectively. Conclusion: ADLis present in the assessment tools. Circular reasoning can occur as disability in ADL can be seen as a predictor, a characteristic, or an outcome of frailty, but also as a predictor of negative health outcomes in the frail. Also, the meaningful concept of the includedADL across various instruments can be interpreted differently.