Objective: Higher intimacy is associated with less behavioral and psychological symptoms of dementia (BPSD) in people with dementia, however, the processes underlying this association remain unclear. This study investigates the role of expressed emotion (EE) and relationship closeness between caregivers and patients with dementia in the manifestation of BPSD.

Methods: We recruited 56 families with dementia and collected 3-month longitudinal data including demographic details of current family caregivers providing care, caregiving relationship closeness (RCS), and BPSD measured using the Neuropsychiatric Questionnaire (NPI-Q). We assessed EE using the validated Family Attitudes Scale (FAS), where higher scores indicate greater intensity of expressed emotion. Correlational and mediation analyses were conducted using baseline and three-month follow-up data to explore the relationships between RCS, EE, and BPSD. Mediation analysis was performed using the SPSS PROCESS Version 4.1 macro. The study received approval from the Institutional Review Board of Osaka University.

Results: Correlation analysis showed that there was significance between RCS and BPSD at baseline and third month (r = –0.301, p < 0.05), and between EE and BPSD (r = 0.378, p < 0.001). Furthermore, mediation analysis demonstrated that caregivers’ EE significantly mediated the association between RCS and BPSD in dementia patients. The indirect effect of RCS on BPSD through caregivers’ EE was found to be significant, with a 95% confidence interval (CI) of (–0.6097, –0.1790), where the CI excludes zero. This indicates that the mediation effect of caregivers’ EE on the relationship between RCS and BPSD is statisticallysignificant.

Conclusions: It suggests that interventions aimed at improving caregiver-patient relationships and managing caregivers’ EE could be crucial in mitigating BPSD, providing a direction for future research and intervention development to support both patients and their families in the dementia care.