Outcome measures for health interventions targeting multimorbid older adults: A systematic review

Background: Older adults with multimorbidity are often excluded from clinical trials. Traditional disease-centered endpoints may be inadequate for this population, presenting unique challenges related to frailty, functional decline and disability. Objectives: To systematically review the literature on outcomes considered relevant in interventions targeting older adults with multimorbidity, based on both patient and healthcare professionals' perspectives. Methods: This systematic review followed PRISMA 2020 guidelines and was registered in PROSPERO (CRD42023478249). We searched five electronic databases for primary quantitative and qualitative studies including patients aged >= 60 years with >= 2 chronic conditions. Outcomes were categorized into six domains: 1) Physical conditions/outcomes; 2) Mental conditions/outcomes; 3) Psychosocial outcomes/general health; 4) Healthcare utilization and costs; 5) Patients' behaviors; 6) Care process outcomes. We conducted a narrative synthesis and compared outcomes across qualitative and quantitative studies. Results: Seventy-one studies were included (53 quantitative, 16 qualitative, 2 mixed-methods). The most frequently reported outcomes fell under Psychosocial outcomes / General health (69.0 %), followed by Care process outcomes (52.1 %) and Healthcare utilization and costs (49.3 %). Qualitative studies more often addressed Mental health outcomes (43.8 %). Maintaining independence, physical function, and quality of life emerged as most important outcomes for older adults. Conclusions: In intervention studies involving older adults with multimorbidity, outcomes should move beyond disease-specific measures to include independence, physical function and quality of life. Outcome selection should account for patient clinical heterogeneity, frailty, and life expectancy to ensure relevance and impact in this complex population.