This review introduces a novel host-centric, trajectory-based framework derived from disablement models that conceptualizes acute respiratory infections as biological stressors interacting with baseline vulnerability. Within this framework, the "trajectory concept" is employed to map heterogeneous recovery patterns in which frailty, multimorbidity, and pre-existing functional impairment outweigh pathogen-specific effects in determining long-term disability.
Drawing on evidence from pneumococcal disease, influenza, respiratory syncytial virus, and COVID-19 in adults aged ?65 years, we identify key biological and clinical mediators, including immunosenescence, inflammaging, acute sarcopenia, delirium, and hospitalization-associated disability that link acute illness to sustained functional loss. Trajectory analyses reveal patterns ranging from rapid recovery to persistent or progressive disability and identify the early post-discharge period as a critical and potentially modifiable window.
Reframing acute respiratory infections as systemic triggers of functional decline shifts clinical priorities from survival to disability prevention. Integrated care models, centered on vaccination, geriatric-informed acute care, comprehensive geriatric assessment, and structured rehabilitation, are essential to preserve independence in ageing populations.
Keywords : Respiratory Tract Infections; Disability Evaluation; Frailty; Functional Status; Aged; Subacute Care