Impact of pre-morbid depression on health-related quality of life in non-demented Parkinson's disease patients.

The need to understand and improve health-related quality of life (Hr-QoL) in Parkinson's disease (PD) has been emphasized. In order to investigate contributions of depression that existed before the onset of typical motor symptoms ("pre-PD depression"), idiopathic non-demented non-psychotic patients with (n = 32) and without (n = 120) a history of pre-PD depression, free of relevant comorbidity, calliper-matched for age, education and disease duration were evaluated for motor and non-motor disease aspects and Hr-QoL (Parkinson's Disease Questionnaire 39, PDQ-39). History of pre-PD depression was independently associated with higher actual levels of depression and anxiety, poorer sleep quality and mental set shifting, which all contributed to poorer Hr-QoL. Mediation analysis demonstrated significant indirect effects (mediated through the effects on mood/emotion/sleep and/or cognition) of pre-PD depression on PDQ summary index and subscales, but also direct (non-mediated) effects on emotional well-being and body discomfort subscales independent of the sociodemographic, motor/non-motor disease or treatment-related characteristics. Data indicate that for a given level of motor/non-motor PD symptoms severity, history of pre-PD depression contributes to poorer Hr-QoL.