Fluctuating pain in Parkinson's disease: Its prevalence and impact on quality of life

Pain is a common non-motor symptom in Parkinson's disease (PD) patients, and the incidence of fluctuating pain may be improved by taking levodopa. There are only a few detailed reports regarding fluctuating pain. In this study, 331 PD patients were classified into three groups: no-pain group (67.4%), non-fluctuating pain group (22.1%), and fluctuating pain group (10.6%). We evaluated patients' background and its impact on the quality of life (QOL) of each group. The pain group exhibited higher levels of depression (p < 0.0001), had a higher frequency of visual hallucinations (p = 0.007), and lower QOL (p < 0.0001) compared with the no-pain group. The fluctuating pain group had a younger onset (p = 0.006), higher Hoehn & Yahr stage (p = 0.018), and higher frequency of wearing-off (p < 0.001) and dyskinesia (p = 0.007) than the other groups. We compared the Parkinson's Disease Questionnaire-8 summary index (PDQ-8 SI) in each pain group to the no-pain group using analysis of variance. As a result, PDQ-8 SI was significantly higher in both the non-fluctuating and fluctuating pain groups (p < 0.0001). Pain is regarded as a non-negligible symptom that affects the QOL of PD patients, and given the unique characteristics, fluctuating pain might be considered as an independent clinical subtype of PD.