Towards a core outcome set (COS) for intrinsic capacity (IC) intervention studies in adults in midlife and beyond: a scoping review to identify frequently used outcomes and measurement tools.

This scoping review was conducted to identify the outcomes and measurement tools used in IC intervention studies, as first step towards the development of a core outcome set (COS) for IC trials. PRISMA-ScR and COS-STAD were followed. The review considered randomized controlled trials targeting IC published in Medline, Scopus, Embase, Cochrane Central Register of Controlled Trials, and clinicaltrials.gov, until June 2023. Of 699 references, 534 studies were screened once duplicates were removed, 15 were assessed for eligibility, and 7 (4 articles and 3 protocols) met eligibility criteria. Twenty-eight outcomes were identified (19 related to IC and its domains and 9 unrelated). The most reported primary outcome was the change in IC levels postintervention (5 over 7 studies) and the most reported outcomes (either as primary and/or secondary) were the changes in physical performance and in depressive symptoms (6 over 7 studies). Fifty-five tools used to construct the domains' z-scores and/or assess the effect of interventions were identified (47 related to IC and its domains and 8 unrelated). The most reported tool was an IC Z-score, calculated by 4 domains' z-scores: locomotor, vitality, cognitive, and psychological (5 over 7 studies). The tools differed among studies (10 locomotor related, 6 vitality related, 16 cognitive related, 8 psychological related, 6 sensorial related, 8 unrelated tools). The vast heterogeneity (28 outcomes and 55 tools within 7 studies) highlighted the need of a COS. These outcomes and tools will be presented to experts in a future step, to select the ones that should be taken into consideration in IC trials.