Protecting the brain from post-stroke cognitive impairment and dementia with multimodal exercise training: study protocol for a Bayesian adaptive trial (PROTECT).

introductionStroke triggers acute vascular and inflammatory mechanisms that predispose the brain to rapid neurodegeneration. Up to 52% of stroke survivors develop cognitive impairment within 6 months and 20% receive a clinical diagnosis of dementia within 5 years. The subacute phase (<6 months) represents a critical window in which the brain may be most responsive to neuroprotective interventions. Multimodal aerobic and resistance training improves cognition in chronic stroke, but whether it improves cognition, neuroimaging markers and blood biomarkers of dementia risk when delivered during this early window remains unknown. The PROTECT trial will compare the effects of 12 weeks of multimodal exercise (moderate-to-high-intensity resistance and aerobic training) versus a low-intensity exercise comparator on cognition, neuroimaging outcomes, blood biomarkers of cognitive decline and dementia risk in people with subacute stroke. METHODS AND ANALYSIS: The PROTECT trial is a 12-week, Phase 3, assessor-blinded, multisite Bayesian adaptive randomised controlled trial (RCT) following a two-arm parallel group sequential design with 6-month and 12-month follow-up (NCT07445841). Participants will be randomised to multimodal training or the comparator using concealed allocation with permuted blocks of varying sizes. The primary outcome is cognition, measured using the 13-item Alzheimer's Disease Assessment Scale-Cognitive assessment (ADAS-Cog-13). Secondary outcomes include ADAS-Cog-Plus, structural and perfusion neuroimaging and blood biomarkers of inflammation and neurodegeneration. Tertiary outcomes include cardiorespiratory fitness, functional mobility, muscle strength, body composition, neuropsychological status, patient-reported cognition, quality of life, fatigue and healthcare utilisation. Outcomes will be assessed at baseline, post-intervention (primary endpoint) and at 6-month and 12-month follow-up. Sample size was estimated via 20 000 Monte Carlo simulations using an ADAS-Cog effect size of Cohen's d=0.63 from a previous exercise RCT. The target was ≥80% power to detect this treatment effect at a one-sided type I error rate of 2.5%, using a weakly informative prior centred at zero with a variance of 100. The minimum required was 45 completers per arm (N=90) and accounting for 25% attrition, up to 120 participants (60 per arm) will be enrolled. Pre-planned adaptive features include: (1) two interim analyses at 50% and 75% of completers; (2) early stopping for efficacy and futility; and (3) sample size re-estimation. ETHICS AND DISSEMINATION: Ethical approval to conduct this study has been granted by the Centre de recherche interdisciplinaire en réadaptation du Montréal métropolitain (CRIR MP-50-2025-2294) and Hamilton Integrated Research Board (HIREB 19222). Any protocol amendments will be submitted to the appropriate ethics boards. Written informed consent to participate in this study will be obtained from all participants by study coordinators or assistants. Study results will be published and reported in peer-reviewed journal following Adaptive Designs Consolidated Standards of Reporting Trials extension guidelines. TRIAL REGISTRATION NUMBER: NCT07445841.