Initiating dopamine agonists rather than levodopa in early Parkinson's disease does not delay the need for deep brain stimulation.

Background And Purpose: While levodopa is the most effective symptomatic treatment for Parkinson's disease (PD), its use is associated with an increased risk of motor complications (MCs) in the first 5 years of treatment compared to dopamine agonist (DA) first therapy. It is not known whether this translates into true benefit later in the disease. We aimed to determine whether there is a difference in the time between initial levodopa versus DA treatment and the development of disabling MCs prompting deep brain stimulation (DBS) consideration.

Methods: This was a retrospective cohort study of patients with PD attending the DBS Clinic at Toronto Western Hospital, Canada between March 2004 and February 2022, who underwent globus pallidus interna (GPI) or subthalamic nucleus (STN) DBS in 2005 or later for disabling MCs.

Results: Of the 438 patients included in the study, 352 underwent STN DBS and 86 underwent GPi DBS. The median (range) disease duration was 9 (2-30) years. The majority of patients (n = 312) received levodopa first and 126 received a DA. There was no significant difference in disease duration or amantadine use between the two groups. The duration from the first treatment to assesment for DBS (levodopa: median 8 years, interquartile range [IQ] 4 years; DA: median 9, IQR 4 years) or DBS surgery (levodopa: median 10 years, IIQR 5 years; DA: median 10 years, IQR 5 years) did not differ.

Conclusion: To our knowledge, this is the only study to date to evaluate the duration between levodopa/DA-first treatment and the development of MCs of sufficient severity to warrant consideration of DBS. No association was found. The results suggest that the development of disabling MCs warranting DBS is independent of the type of first dopaminergic treatment.