What are the most important nonmotor symptoms in patients with Parkinson's disease and are we missing them?

Nonmotor symptoms (NMS) are increasingly recognized as important and neglected aspects of Parkinson's disease (PD). We evaluated their relative frequency and comparative impact on health-related quality of life (Hr-QoL) using validated questionnaires. In addition, we assessed the rate of reporting of NMS in neurology clinics compared with their subjective impact on patients. We used a range of validated clinimetric scales of motor and nonmotor symptoms and Hr-QoL to assess consecutive patients with PD. Reporting of NMS was assessed by comparison with case note documentation. A mean of 11 of 30 NMS per patient were elicited on the NMS questionnaire of which on average 4.8 were reported in the clinical notes (44%). The most common NMS were autonomic (particularly urinary). The Hr-QoL scores correlated most strongly with autonomic dysfunction (r = 0.84; particularly urinary and gastrointestinal symptoms), mood (r = 0.74), fatigue (r = 0.74), sleep problems (nocturnal r = 0.55; daytime somnolence r = 0.65), pain (r = 0.56), and psychosis (r = 0.55, all p < 0.0001) followed by UPDRS motor score (r = 0.48, p < 0.0001). Greater motor fluctuations (r = 0.57) and dyskinesia (r = 0.43, both p < 0.0001) were also associated with worse Hr-QoL. In multivariate analysis, depression had the strongest association with Hr-QoL (adjusted R(2) = 0.53, p = 0.005) followed by fatigue, thermoregulatory, gastrointestinal, and cardiovascular autonomic function (especially orthostatic hypotension), daytime somnolence, and urinary problems. This study demonstrates that a autonomic dysfunction, psychiatric complications, pain, fatigue, and sleep problems are major correlates of poor Hr-QoL. However, whilst psychiatric problems are increasingly documented, many symptoms (particularly those possibly perceived as embarrassing or unrelated) remain under-reported.