Objectives: To clarify the frequency of wearing-off phenomenon (WO) and the validity of the Chinese version of the 9-item wearing-off questionnaire (CWOQ-9) in WO identification in this large population.
Methods: Parkinson's patients treated with antiparkinsonian medications were consecutively recruited into this observational, cross-sectional investigation. Patients completed the CWOQ-9 prior to the independent clinician assessment.
Results: A total of 1,385 patients were included in the analysis. The mean age was 69.7 ± 9.5 years and the mean disease duration was 5.8 ± 4.7 years. Clinicians identified WO in 763 patients, with an overall prevalence of 55.1%. In patients within 1 year of disease duration, clinicians diagnosed WO in eight patients, with a percentage of 12.9%. With the disease progression, the WO frequency gradually increased to 76.2% in patients with 10–15 years of disease duration. Then, it slowly decreased at a longer disease duration. The occurrence of WO was closely associated with the disease duration, H&Y staging, and levodopa daily dose. CWOQ-9 identified 1,071 patients (1071/1398, 77.33%) that had WO-related symptoms. The mean CWOQ-9 score was 3.4 ± 1.6. CWOQ-9 corresponded with clinician assessments of WO in 734 of 763 cases; clinicians disagreed with the CWOQ-9 considering the presence of WO in 337 of 1,071 cases. The sensitivity and specificity of CWOQ-9 were 96.2 and 45.8%, respectively.
Conclusions: WO occurred frequently at the early and middle stage of PD. CWOQ-9 was qualified as a pre-visiting screening tool for clinicians to better identify WO.