Parkinson’s disease (PD) is a neurodegenerative disorder affecting over 10 million people worldwide. PD is characterized by both motor (e.g., tremor, rigidity, and bradykinesia) and non-motor (including cognitive impairment and neuropsychiatric symptoms such as apathy, disinhibition, executive dysfunction) symptoms. Caregiver burden is prevalent in those providing care for patients with PD and can result in negative health complications. Past work shows associations between motor symptoms, cognitive impairment, neuropsychiatric symptoms, and caregiver burden in PD. However, their relative contributions are poorly understood. This study examined these relationships, hypothesizing that while motor symptoms, cognitive impairment, and neuropsychiatric symptoms would all affect caregiver burden, neuropsychiatric symptoms would predict burden above and beyond the contribution of the other factors

Participants were 42 people living with PD who were assessed at a hospital-based tertiary movement disorders specialty clinic for deep brain stimulation (DBS) candidacy evaluation with their caregiver. Motor exam was assessed by a PD specialist using the Unified Parkinson’s Disease Rating Scale (UPDRS). The Mini Mental State Examination (MMSE) assessed global cognition. Frontal Systems Behavior Scale (FrSBe) Family Form captured caregiver ratings of neuropsychiatric symptoms under 3 subscales: apathy, disinhibition, and executive dysfunction. The Multidimensional Caregiver Strain Index (MCSI) captured caregiver burden. Linear regression analyses examined relationships between caregiver burden (MCSI) and motor symptoms (UPDRS), cognitive impairment (MMSE), and neuropsychiatric symptoms (FrSBe).

Using linear regression analyses, cognitive impairment (R2=0.08, F(1,41)=4.42, p=0.04) and neuropsychiatric symptoms (R2=0.35, F(1, 41)=21.0, p<0.01) predicted caregiver burden but motor symptoms did not (R2=0.03, F(1,41)=1.30, p=0.26). Hierarchical linear regression revealed that neuropsychiatric symptoms predicted caregiver burden above and beyond the contribution of cognitive impairment (AR2=0.28, AF(1)=12.7, p=0.001), accounting for an additional 28% of the variance in caregiver burden. Follow-up linear regression to examine the relationships between caregiver burden and the FrSBe subscales indicated that apathy (p<0.001), versus disinhibition (p=0.16) and dysexecutive behaviors (p=0.80), was the driver of the significant relationship.

Consistent with our hypothesis, results revealed that cognitive impairment and neuropsychiatric symptoms (specifically apathy) were independent predictors of caregiver burden, with neuropsychiatric symptoms predicting caregiver burden above and beyond the contribution of cognitive impairment. Somewhat surprisingly, motor symptoms were not a predictor of caregiver burden contrary to some previous research, though findings are mixed. Results highlight the importance of assessing for neuropsychiatric symptoms in PD, which may be overlooked by care providers relative to motor or cognitive symptoms, but which appear stressful to caregivers. Future directions include reexamining results in a larger more heterogenous sample including people living with PD at different disease stages (i.e., everyone in the present sample had severe enough symptoms to be considering DBS). Cognitive measures of executive functioning (which are more specific to PD than measures of global cognition) should also be included in future works. Development of supportive caregiver interventions specifically targeting apathy in PD may be useful. Longitudinal designs would be helpful to reexamine relationships following DBS surgery, as there are some reports of increased neuropsychiatric symptoms following the procedure.