The non-motor side of the honeymoon period of Parkinson's disease and its relationship with quality of life: a 4-year longitudinal study

Background and purpose: Very little is known about the progression of non-motor symptoms (NMSs) in Parkinson's disease (PD) and there are no longitudinal studies exploring this topic from the earliest stage, when patients receive the diagnosis. We here report on the progression of NMSs over 4 years from diagnosis in a cohort of de-novo, previously untreated, patients with PD. Methods: Consecutive de-novo (disease duration < 2 years), untreated patients with PD were enrolled in this observational study. Evaluations were then scheduled every 2 years and included assessment of motor and non-motor features as well as of quality of life measures. Results: Sixty-one patients were prospectively followed-up for 4 years from diagnosis. The majority of NMSs increased over time and significantly affected quality of life, whereas motor disability did not. There was no significant association between NMSs and dopaminergic therapy in terms of both drug class and total levodopa-equivalent daily dosage. Excessive daytime sleepiness was the only NMS correlating with therapy with dopamine agonists. Female patients were more likely to have worse quality of life. Conclusions: Non-motor symptoms significantly increase over time, with a different progression rate for each one. NMSs significantly affect quality of life in PD and we here demonstrated that this was especially the case when patients were in their (motor) honeymoon period. Future trials should target non-dopaminergic networks and consider NMSs in their outcomes.