Behavioural and psychological symptom determinants of carer burden across clinical syndromes associated with frontotemporal lobar degeneration and Alzheimer’s disease: a transdiagnostic analysis

BACKGROUND: This study characterised overall transdiagnostic associations between psychological and behavioural symptoms and carer burden, and examined syndrome-specific contributions across clinically probable FTLD and AD groups. METHODS: A total of 432 individuals with clinically probable FTLD and AD were included. The primary analytic cohort comprised 358 participants with complete carer burden data, including 230 and 128 individuals in the FTLD and AD diagnostic groups, respectively. Behavioural and psychological symptoms were assessed using the Cambridge Behavioural Inventory-Revised (CBI-R). Carer burden was measured with the Zarit Burden Interview (ZBI). Longitudinal CBI-R and ZBI data were analysed in 172 participants with available ZBI data at both baseline and follow-up (mean interval ≈ 1 year). RESULTS: Behavioural rigidity (standardised β = 0.15, 95% CI [0.03, 0.28], p = 0.015) and apathy (standardised β = 0.14, 95% CI [0.02, 0.26], p = 0.020) showed the strongest associations with carer burden overall. Behavioural rigidity was salient in the FTLD group (standardised β = 0.18, 95% CI [0.02, 0.33], p = 0.024), whereas apathy (standardised β = 0.26, 95% CI [0.04, 0.47], p = 0.021) and abnormal behaviour (standardised β = 0.26, 95% CI [0.05, 0.48], p = 0.018) were salient in the AD group. Longitudinal increases in mood-related symptoms (standardised β = 0.24, 95% CI [0.001, 0.48], p = 0.048) predicted greater carer burden at follow-up. CONCLUSIONS: Our findings highlight the relevance of symptom-focussed strategies for managing carer burden across dementia syndromes. Group-specific analyses suggest prioritising behavioural rigidity in FTLD syndromes and apathy and abnormal behaviour in AD subtypes, while timely management of changes in mood symptoms may help alleviate carer burden over time.