Nonmotor predictors for levodopa requirement in de novo patients with Parkinson's disease

The variability in the clinical phenotype of Parkinson's disease (PD) suggests the existence of several subtypes of the disease. Motor heterogeneity of PD is well established, but not nonmotor heterogeneity. At present, we are unable to predict the rate of progression of PD based on robust biomarkers. We aimed to examine the heterogeneity of PD by attempting to identify nonmotor factors associated with the rate of motor progression and functional decline, as measured by the time to reach the need for levodopa therapy during the first 4 years from diagnosis in a cohort of de novo PD patients. The median time to introduction of L-dopa for patients with urinary symptoms was significantly shorter than that for those without (20 vs. 37 months; P = 0.001). Cox's regression models showed that the urinary domain was associated with a higher probability of starting L-dopa (hazard ratio: 2.1; P = 0.002). There was no influence of such confounders as sex, age, baseline motor features, use of dopamine agonists and/or monoamine oxidase B inhibitors, and total L-dopa equivalent daily dosage. Patients with urinary symptoms had higher baseline and follow-up motor and nonmotor disturbances than those without. Our study suggests the existence of a subgroup of patients who show urinary symptoms along with an overall higher motor and nonmotor burden. Such patients are prone to manifest a rapid functional decline over the first 4 years of the disease. Urinary symptoms might be a clinical marker of severity as well as a possible nonmotor subtype of PD.