Multiphase optimization of a multicomponent intervention for informal dementia caregivers: a study protocol

BACKGROUND: Family caregiver interventions are essential to support dementia caregiving. However, such interventions are typically complex and consist of multiple components. Existing evidence rarely delineates the effectiveness and interactions between individual components. To optimise intervention, we adopt the multiphase optimisation strategy (MOST) to test the implementation fidelity and determine the effect of each component and the interactions between each component and the corresponding outcome. METHODS: A prospective, assessor-blinded, randomised clinical trial with fractional factorial design using the MOST principle. Two hundred fifty family dementia caregivers will be randomised to one of 16 experimental conditions in a fractional factorial design involving six intervention components: (1) dementia and caregiving education; (2) self-care skills; (3) behavioural symptom management; (4) behavioural activation; (5) modified mindfulness-based cognitive therapy; and (6) support group. The first one is the core component, and the five remaining will be examined. Physical health, caregiver burden, stress, psychological well-being, anxiety and depressive symptoms, and social support will be assessed over the 12-month study period. Following the intention-to-treat principle, linear mixed models and regression analyses will be used to examine the specific effect of the five components and their two-way interactions to propose the most effective combination. DISCUSSION: This is the first study adopting the multiphase optimisation strategy to identify the most active and engaging components of a psychological intervention for caregivers of patients with dementia. In view that dementia caregiver interventions are increasingly diversified and complex, such knowledge is important to maximise the intervention efficacy and allow the intervention to be implemented within an efficient timeframe and dosage. The optimisation of caregiver support interventions is critical to enhance the health outcomes of caregivers and care recipients, thereby, delaying possible institutionalisation and reducing the costs of long-term dementia care. TRIAL REGISTRATION: This study was retrospectively registered in the WHO Primary Registry – Chinese Clinical Trials Registry (ChiCTR2300071235). (Protocol date 30/10/2020; version identifier 2020–2021-0045). Registered on 9 May, 2023. REPORTING METHOD: SPIRIT guideline was followed. PATIENT OR PUBLIC CONTRIBUTION: No patient or public involvement. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13063-023-07801-3.