A body of literature now exists, which demonstrates that idiopathic Parkinson's 
disease (PD) has a major negative impact on quality of life (QoL), and that 
depression and cognitive impairment are among the main predictors of poor QoL in 
this disorder. Relatively little work has been done to assess the differential 
contribution of the specific symptoms of PD to QoL, which was the aim of this 
study. One hundred thirty patients with PD completed a booklet of 
questionnaires, which included the PDQ39 as a disease-specific measure of QoL, a 
symptom checklist, a mobility checklist, as well as patient ratings of disease 
stage and disability. The results indicated that the contribution of physical, 
medication-related, and cognitive/psychiatric symptoms to QoL can be 
significant. Sudden unpredictable on/off states, difficulty in dressing, 
difficulty in walking, falls, depression, and confusion were PD symptoms, which 
significantly influenced QoL scores. Among the mobility problems associated with 
PD, start hesitation, shuffling gait, freezing, festination, propulsion, and 
difficulty in turning had a significant effect on QoL scores. In addition to 
depression and anxiety, the major predictors of QoL were shuffling, difficulty 
turning, falls, difficulty in dressing, fatigue, confusion, autonomic 
disturbance particularly urinary incontinence, unpredictable on/off 
fluctuations, and sensory symptoms such as pain. The implications of these 
results for the medical management of PD are discussed.