Clinical phenotype and risk of levodopa-induced dyskinesia in Parkinson's disease

It is unclear whether patients with different clinical phenotypes of Parkinson's disease (PD) differ in their risk of developing levodopa-induced dyskinesia. We evaluated the possible association between clinical phenotypes and risk of levodopa-induced dyskinesia in PD patients using a case-control design. The FRAGAMP study is a large Italian multicenter study. Patients affected by PD diagnosed according to the Gelb's criteria were enrolled and underwent a face-to-face interview. Clinical scales were used to evaluate motor and cognitive impairment. Presence of dyskinesia was assessed by the item 32 of the UPDRS section IV. On the basis of the most prominent motor symptoms at onset PD, patients were classified as tremor-dominant, akinetic-rigid, or mixed type. 485 PD patients (292 men; mean age 65.6 ± 9.8) were enrolled in the study of whom 128 (26.4 %) presented levodopa-induced dyskinesia. Of the 485 patients, 311 (64.1 %) were classified as tremor-dominant, 104 (21.4 %) as Akinetic-Rigid and 70 (14.4 %) as mixed type. Multivariate logistic regression analysis showed a significant negative association between tremor-dominant phenotype and levodopa-induced dyskinesia (adjusted OR 0.48; 95 % CI 0.23-1.00; p value 0.05). When analysis was stratified by age at onset a stronger negative association was found among the late onset (>50 years) PD patients (OR 0.28; 95 % CI 0.11-0.70; p value 0.007) while no association was found among patients with an early onset. Our findings support the hypothesis that the occurrence of resting tremor as an initial manifestation of PD may predict a lower probability of developing levodopa-induced dyskinesia.