The goal of this study is to evaluate whether the Cognitive Model for Behavioral Interventions (CoMBI), a person-centered, non-pharmacological intervention, can reduce behavioral and psychological symptoms of dementia (BPSD) in people with dementia living in nursing homes. The study also aims to examine whether CoMBI can reduce caregiver burden and improve quality of life in people with dementia.

The main questions it aims to answer are:

Does CoMBI reduce the severity of behavioral and psychological symptoms of dementia compared to care as usual?

Does a reduction in BPSD lead to lower caregiver burden and improved quality of life for people with dementia?

Do personal factors, such as personality (dys)functioning, gender, level of cognitive impairment and stage of dementia, influence the effectiveness of CoMBI?

Researchers will compare CoMBI to care as usual to determine whether CoMBI leads to better outcomes for people with dementia and their caregivers.

Participants will:

Receive care in residential long-term care facilities where care staff are trained to apply CoMBI.

Be observed and assessed repeatedly over time as part of a stepped-wedge cluster randomized trial design.

Behavioral and Psychological Symptoms of Dementia (BPSD), also referred to as neuropsychiatric symptoms, are highly prevalent across all types of dementia and represent a major clinical and societal challenge. These symptoms are associated with accelerated disease progression, reduced quality of life for people with dementia, and substantial burden for both formal and informal caregivers. In residential long-term care facilities, where BPSD are particularly common, management often relies heavily on psychotropic medication despite risks, including increased morbidity and mortality. International guidelines therefore recommend person-centered, non-pharmacological interventions as first-line treatment. However, existing non-pharmacological approaches show mixed effects, face implementation barriers, and often insufficiently account for individual differences such as premorbid personality, despite growing evidence that personality plays a key role in the development and severity of BPSD.

The Cognitive Model for Behavioral Interventions (CoMBI) is a person-centered, non-pharmacological intervention designed to address these limitations. CoMBI is grounded in the assumption that BPSD partly emerge when underlying core needs are insufficiently met. These core needs are shaped by premorbid personality characteristics and are activated by specific environmental triggers. Drawing on Beck's cognitive model of personality disorders and nursing interventions from the Nursing Intervention Classification, CoMBI distinguishes distinct personality profiles, each associated with characteristic unmet needs and triggering situations. For each profile, tailored intervention strategies have been developed to compensate for unmet needs by modifying environmental factors and caregiver responses.

The CoMBI training provides caregivers with a structured framework to understand BPSD in relation to premorbid personality and unmet core needs. Care staff are trained to assess BPSD, identify personality-related core needs and triggering events, and implement tailored interventions. This is well documented in a CoMBI care plan, specifying which interventions will be applied and the desired behavioral outcomes. The care plan can be reevaluated every care team meeting.

To empirically demonstrate the effectiveness of CoMBI, we will conduct a stepped-wedge cluster randomized trial (SW-CRT) with repeated measures. All units of the participating nursing homes will initially receive care as usual (CAU) and will sequentially transition to the CoMBI condition. Outcome measurements will be conducted every four weeks, including at the time each unit changes from CAU to CoMBI. Outcomes are assessed using the Neuropsychiatric Inventory Questionnaire (NPI-Q), the Global Deterioration Scale (GDS), Qualidem and the Montreal Cognitive Assessment (MoCA). To properly identify the core needs for CoMBI, two personality questionnaires will be administered, namely the Personality Inventory for DSM-5 Brief Form + Modified (PID-5-BF+M) and the Level of Personality Functioning Scale Brief Form 2.0 (LPFS-BF 2.0).

Inclusion Criteria:

• Being a resident in a participating nursing home
• Having a formal diagnosis of neurocognitive disorder (NCD) accord-ing to DSM-5-TR (e.g. Alzheimer's disease, NCD with Lewy Bodies, Vascular NCD, …) or a medical record indicating probable dementia
• Presence of one or more BPSD symptoms at moment of inclusion in the study (measured with the NPI-Q at baseline). Symptoms measured by the NPI-Q include delusions, hallucinations, agitation/aggression, depression/dysphoria, anxiety, euphoria/elated mood, apathy/indifference, disinhibition, irritability/lability, aberrant motor behavior, nighttime behavior disturbances/sleep disturbances, and changes in appetite and eating behavior.
• Primary caregivers (i.e. nurses providing daily care) and patient's representative and/or a close relative/friend (i.e. informant who will fill in the premorbid personality questionnaire) are proficient in Dutch (i.e., are able to fill in the questionnaires)
• The informant who fills in the premorbid personality questionnaire knows the patient well from before the onset of neurocognitive problems
• As individuals with dementia are often legally incapacitated, informed consent will be obtained prior to participation from the resident when competent to consent, or otherwise from the resident's legal representative when legally incompetent.

Exclusion Criteria:

Exclusion criterion for nursing homes is:

- Already applying a structured (theory-based) behavioral counseling as CAU.