Background: although non-motor symptoms of Parkinson's disease (PD) are known to adversely affect disability and health-related quality of life, the impact that specific disorders of reward and motivation have remains unclear. Impulse control disorders are more likely in those with a younger disease onset although there is no strong evidence to date that apathy is related to age of onset or correlated with a longer duration of disease.
Objective: to examine the effects of apathy and impulse controls disorders on disability and health-related quality of life.
Methods: a total of 99 non-demented participants with PD (35 with impulse control disorders, 26 with apathy and 38 with neither behavioural complication) were assessed using the Unified Parkinson's Disease Rating Scale (Activities of Daily Living component) and the Schwab-England scale to evaluate disability, and the PDQ (eight items) to assess quality of life.
Results: quality of life was reduced in both behavioural groups compared with participants without either condition. Disability was greater in the group with apathy. Variation in disability score (56%, P < 0.001) was explained by greater levels of apathy, depression, motor impairment and longer disease duration. Variation in quality of life score (54%, P < 0.001) was explained by higher levels of impulsivity, depression, dopaminergic load, motor complications, working memory problems and younger age at onset.
Conclusion: apathy and impulsivity negatively impact on disability and health-related quality of life, emphasising the importance of effective diagnosis and management of these PD-related behavioural disturbances.