Introduction

Multimorbidity, defined by the WHO as the coexistence of two or more chronic conditions,1 is a growing challenge for public health globally. Lower quality of life, psychological distress, long hospital stays, postoperative complications, high costs of care and elevated mortality are becoming an enormous burden for patients and their families as the prevalence of multimorbidity increases along with the ageing population.2 To deliver adequate and cost-effective care for patients with multimorbidity, healthcare needs to transition from traditional single-disease management to a patient-centred approach to managing complex health needs.3

A randomised controlled trial (RCT) is considered the gold standard in the evaluation of health interventions. High-quality evidence from RCTs is crucial for the management of comorbidities and health in general in populations with multimorbidity.4 However, the evidence remains sparse. Clinical trials commonly exclude patients with multimorbidity to reduce bias, and the applicability of the findings for patients with different comorbidities is not addressed.5 Conversely, since multimorbidity is common in elderly people, it can be expected that most participants in trials among elderly populations have several underlying comorbidities. However, the comorbidities and their interactions are not necessarily fully considered in the analyses and it may be questionable whether and how the results apply to patients with …