Background: Dementia in the oldest-old is projected to increase exponentially as is the burden of their caregivers who may experience unique challenges and suffering. Thus, we aim to investigate which factors are associated with older caregivers' burden in caring demented outpatients in a multicenter cohort.

Methods: Patients and their caregivers, both aged ≧65 years, in the National Dementia Registry Study in Taiwan (T-NDRS) were included in this study. Caregiver burden was measured with the short version of the Zarit Burden Interview (ZBI). The correlations between the ZBI scores and characteristics of caregivers and patients, including severity of dementia, physical comorbidities, instrumental activities of daily living (IADL), neuropsychiatric symptoms assessed by the Neuropsychiatric Inventory (NPI), and family monthly income, were analyzed.

Results: We recruited 328 aged informal caregiver-patient dyads. The mean age of caregivers was 73.7 ± 7.0 years, with female predominance (66.8%), and the mean age of patients was 78.8 ± 6.9 years, with male predominance (61.0%). Multivariable linear regression showed that IADLs (β = 0.83, p < 0.001) and NPI subscores of apathy (β = 3.83, p < 0.001)and irritability (β = 4.25, p < 0.001) were positively associated with ZBI scores. The highest family monthly income (β = - 10.92, p = 0.001) and caregiver age (β = - 0.41, p = 0.001) were negatively correlated with ZBI scores.

Conclusions: Older caregivers of older demented patients experience a higher care burden when patients had greater impaired functional autonomy and the presence of NPI symptoms of apathy and irritability. Our findings provide the direction to identify risky older caregivers, and we should pay more attention to and provide support for these exhausted caregivers.