Impact of POPulation Medicine Multimorbidity Intervention in Xishui County (POPMIX) on people at high risk for COPD who smoke: Protocol of the POPMIX-Smoking cluster-randomized controlled trial

Background Tobacco use is a major contributor to the burden of chronic obstructive pulmonary disease (COPD) and other non-communicable diseases (NCDs) in China. High-risk smokers—particularly those with pre-existing chronic conditions—often remain underserved by conventional smoking cessation programs. Population medicine offers a promising framework for proactively identifying high-burden diseases, managing multimorbidity, and prioritizing interventions for vulnerable populations. Methods This protocol describes a stratified, two-arm cluster randomized controlled trial (cRCT) conducted in Xishui County, Guizhou Province. A total of 26 townships were stratified by population size and randomly assigned in a 1:1 ratio to receive either a multi-component intervention or usual care. Eligible participants were high-COPD-risk smokers aged 35 years or older, screened using the COPD Screening Questionnaire. The intervention includes digital smoking cessation and mental health support, community-based spirometry, tailored chronic disease management, and a pay-for-population mechanism incentivizing providers. Primary outcomes are smoking amount and nicotine dependence, and secondary outcomes include COPD-related health outcomes, hypertension, diabetes, health risk behaviors, quality of life, healthcare utilization, and productivity loss. Follow-up occurs at three, six, and 12 months. Discussion The trial addresses a critical gap in tobacco-related NCD prevention in rural China. By combining behavioral, clinical, and digital health components, and by integrating incentive-aligned delivery through pay-for-population, the intervention aims to demonstrate a scalable, sustainable population medicine strategy. The focus on multimorbidity and early intervention among high-COPD-risk smokers reflects an essential evolution in rural public health practice. Trial registration This trial was registered at clinicaltrials.gov. ClinicalTrials.gov Identifier: NCT06458205. Registered on June 9, 2024.