Clarifying healthy aging: building a common language for policy innovation within the Age-It Research Program

Objectives: This study aimed to map and classify the definitions of "healthy ageing" (HA) employed in randomized controlled trials (RCTs) over the past decade, and to identify conceptual and methodological trends, with the goal of informing future research and policy efforts toward harmonization. Methods: A systematic review of HA definitions was conducted according to the PRISMA guidelines. A search strategy was designed, refined, and executed using Medline (Ovid) up to July 19, 2024. The primary search term was "healthy aging," with results filtered specifically for RCTs. Results: Of 38,219 records initially retrieved, 1,588 were screened, and 48 met the inclusion criteria. No unified definition of HA was identified. Instead, three main types emerged: (a) multidimensional definitions with qualitative assessments (29.2%), (b) multidimensional definitions with quantitative assessments (27.0%), and (c) condition- or disease-specific definitions (43.8%). The most common intervention targets were active aging (29.2%), nutritional supplementation (14.6%), cognitive decline (12.5%), and physical activity (12.5%). Considerable heterogeneity was observed in the domains (e.g., physical, cognitive, psychological, and social) and the tools used to assess HA. Discussion: The findings highlight substantial conceptual variability in how HA is defined and measured in RCTs. This diversity reflects the multidimensional and context-dependent nature of HA but poses challenges for synthesis and comparison across studies. A shared framework for defining HA in interventional research is needed to support evidence-based aging policies. By mapping the range of operational definitions used in RCTs, this review provides a foundation for standardizing future HA research.