Non-motor symptoms depending on motor severity in Japanese patients with Parkinson's disease: A multicenter cross-sectional study

Background: Although non-motor symptoms (NMS) in patients with Parkinson's disease (PD) often worsen as the severity of motor symptoms (MS) increases, few studies have assessed the associated factors of non-motor symptoms. Objective: This study aims to determine whether the presence of NMS in PD patients is associated with or independent from the severity of MS considering confounders. Methods: The registry of PD patients from seven facilities in Japan was used. Multiple logistic regression was performed with each domain and item of the Non-motor Symptoms Scale (NMSS) as objective variables. Severity of motor symptoms was assessed by Hoehn & Yahr stage (HY stage) as an explanatory variable. The analysis was adjusted for sex, age, disease duration, presence/absence of wearing off and dyskinesia, clinical phenotypes and Levodopa equivalent daily dose. Results: A total of 1037 patients were analyzed. Analysis by NMSS domain showed higher odds ratios (ORs) in patients with higher HY stages compared with patients with lower HY stages for domains D1 (cardiovascular), D2 (sleep/fatigue), D3 (mood/apathy), D4 (perceptual problems/hallucinations), D5 (attention/memory), and D6 (gastrointestinal) (ORs: 1.54-2.72, P < .05). However, only domains D7 (urinary) and D8 (sexual dysfunction) were not associated with HY stage. Item 2 (fainting) and Item 14 (delusions) showed higher ORs in the HY stage 4-5 (ORs: 9.95 and 5.92, P < .05). Conclusions: Most NMS worsened with exacerbation of MS in PD patients, however some NMS domains were also affected with other factors. These findings contribute to the understanding of the clinical picture of PD and may improve personalized medicine and research in PD.