# The complexity of outcome measure selection within multiple long-term condition research: an analysis of exercise-based rehabilitation trials

## TL;DR

This study examines outcome measures in exercise-based rehabilitation trials for people with multiple long-term health conditions and finds partial alignment with a core outcome set.

## Contribution

The study maps exercise-based rehabilitation trial outcomes to a core outcome set for multimorbidity, revealing gaps in specific domains.

## Key findings

- Exercise capacity and health-related quality of life were the most commonly reported outcome domains in MLTC trials.
- Only partial alignment with the COSmm domains was observed, with communication and healthcare quality domains missing.
- Outcome measures in MLTC trials showed some similarity to those used in single LTC trials.

## Abstract

Consistent evidence has demonstrated the health benefits of exercise-based rehabilitation across various long-term conditions (LTC); however, evidence in people with multiple LTC (MLTC; or ‘multimorbidity’) is unclear. Development and evaluation of these interventions for MLTC requires a consensus on relevant outcome measures. We aimed to map the outcomes collected and reported in trials of exercise-based rehabilitation in people with MLTC to an existing core outcome set for MLTC (COSmm), and compare to outcomes reported in exercise-based rehabilitation trials of single LTC.

A secondary analysis of two systematic reviews assessing exercise-based rehabilitation in MLTC. Outcome measures within included trials were categorised into domains and mapped to the existing COSmm. Domains and measures were also extracted from an overview of systematic reviews investigating exercise-based rehabilitation across single LTC.

Two hundred seventeen outcome measures across 59 trials of exercise-based rehabilitation for MLTC were identified. The most common domains were exercise capacity (26 outcomes across 41 trials (69.5%)) and health-related quality of life (18 outcomes across 35 trials (59.3%)). Mapping to COSmm showed consistency in the collection and reporting of outcomes in the domains of physical function, health-related quality of life, mental health, and intervention adherence. However, no outcome measures could be mapped to domains of communication, shared decision-making, prioritisation, or quality healthcare. Analysis of the overview of systematic reviews across single LTC found heterogeneity in outcome measures with common measures being relatively similar to those reported in MLTC populations.

Current outcomes collected and reported in published trials of exercise-based rehabilitation for MLTC appear to only partially map to the domains of the COSmm. This review highlights the need to consider the specific core outcome set domains needed for collection in future trials of intervention for MLTC including exercise-based rehabilitation.

The online version contains supplementary material available at 10.1186/s13063-025-09363-y.