Concepts to be considered when appraising applicability of evidence to older people - generalisability

Definition

Generalisability - the extent to which a study's findings, typically derived from a trial population, can be validly applied to a different population such as frail older patients - a critical appraisal concept given how often older, multimorbid, and frail patients are excluded from major trials

Older adults, and particularly frail or cognitively impaired older adults, are systematically underrepresented in clinical trials relative to their share of real-world disease burden
Trials commonly exclude patients with significant comorbidity, polypharmacy, cognitive impairment, or limited life expectancy - precisely the characteristics common in the geriatric patients the results may then be applied to in practice, creating a generalisability gap

Before applying a trial result to an individual older patient, explicitly ask whether that patient resembles the trial population (age, comorbidity burden, functional status, frailty) or differs from it in ways that could change the expected benefit-harm balance

Where good evidence in a frail/elderly population is lacking, extrapolation from younger/fitter trial populations should be done cautiously, with explicit acknowledgement of the uncertainty, rather than applied as if directly equivalent
Absolute risk/benefit (not just relative risk reduction) should be considered, since absolute benefit is often smaller in older patients with a shorter life expectancy and more competing risks, even when relative benefit is preserved

Evidence-based medicine in geriatric practice, trial exclusion criteria, extrapolation of evidence to underrepresented populations

The absence of trial evidence specifically in frail older adults is not evidence of absence of benefit or harm - it reflects a genuine evidence gap that requires clinical judgement to navigate, not a reason to withhold treatment reflexively

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