The concept of disability and its causal mechanisms in older people over time from a theoretical perspective: a literature review.

Ageing with a disability increases the risk of hospitalization and nursing home admission. Ageing in place interventions aiming to reduce disability are often not sufficiently effective and inadequately theory-based. There are many models available on disability, but it is unclear how they define disability, what their differences are, and how they evolved throughout the years. This paper aims to provide an overview of the evolution of these models and to elaborate on the causal mechanisms of disability. A literature review was conducted as part of the TRANS-SENIOR international training and research network. PubMed and Google Scholar were searched, and snowball sampling was applied to eligible publications. Data were extracted from the included publications, and a thematic analysis was performed on the retrieved data. Overall, 29 publications were included in the final sample. All included models arose from three original models and could be divided into two types: linear models and models on the interaction between the person and the environment. Thematic analysis led to three distinct evolutionary trends: (1) from a unidirectional linear path to a multidirectional nonlinear path, (2) from the consequences of disease towards the consequences of person-environment interaction, and (3) from disability towards health and functioning. Our findings suggest that by optimizing the use of personal as well as environmental resources, and focusing on health and functioning, rather than disability, an older person's independence and wellbeing can be improved, especially while performing meaningful daily activities in accordance with the person's needs and preferences.