Exploration of the longitudinal clinical course and potential prognostic factors in Parkinson's disease: 2.5-year observational study in Japan.

Background: Several long-term studies have characterized the course of Parkinson's disease (PD) outside Japan, but few have been conducted in Japan. This study aimed to explore the longitudinal clinical course of PD symptoms in patients receiving standard therapy in Japan and to identify potential factors associated with clinically relevant worsening. Methods: This study used data from 348 patients with PD at Juntendo University Hospital, Japan. Baseline characteristics and longitudinal clinical status, including the Unified Parkinson's Disease Rating Scale (UPDRS) motor scores, were obtained and summarized. Factors potentially associated with clinically relevant worsening were also explored. Results: Among 194 analyzed patients, the study population predominantly had mild to moderate PD, with a mean age of 66.4 years, mean disease duration of 6.22 years, mean UPDRS III score of 20.0, and mean Hoehn and Yahr stage of 2.2. Most patients were receiving L-dopa (88.7%), with a mean daily dose of 477.0 mg. The mean UPDRS III score improved by 3.3 points at the 6-month visit and remained relatively stable for up to 2.5 years. In multivariate exploratory analyses, baseline motor severity, time from PD onset to referral, and orthostatic hypotension were associated with clinically relevant worsening. Conclusion: Our findings suggest that timely referral to specialized care and assessment of autonomic symptoms, particularly orthostatic hypotension, may help identify patients at higher risk of clinically relevant worsening in routine PD care.