Axial symptoms predict mortality in patients with Parkinson disease with subthalamic stimulation

Objective: To characterize how disease progression is associated with mortality in a large cohort of PD patients with long-term follow-up after STN-DBS. Methods: Motor and cognitive disabilities were assessed before, and 1, 2, 5 and 10 years after STN-DBS in 143 consecutive PD patients. We measured motor symptoms Off and On levodopa and STN-DBS, and recorded causes of death. We used linear mixed-models to characterize symptom progression, including interactions between treatment conditions and time to determine how treatments changed efficacy. We used joint models to link progression to mortality. Results: Median observation time was 12 years after surgery, during which akinesia, rigidity and axial symptoms worsened, with mean increases of 8.8 (SD 6.5), 1.8 (3.1) and 5.4 (4.1) points from year 1 to 10 after surgery (On dopamine/On STN-DBS), respectively. Responses to dopaminergic medication and STN-DBS were attenuated with time, but remained effective for all except axial symptom...