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August 27, 2014
New Dopamine Therapy Linked to Impulse Control
Disorder, Sleepiness Philadelphia—The initiation of dopamine-replacement therapy is associated with increasing frequency of impulse-control disorder and excessive daytime sleepiness, according to the first longitudinal study to come out of the Parkinson’s Progression Markers Initiative (PPMI). The study, led by University of Pennsylvania researchers, also notes that neuropsychiatric symptoms such as depression, anxiety, and fatigue are more common in newly diagnosed Parkinson’s disease (PD) patients compared to the general population. The report was published recently in the journal Neurology. The PPMI is a multicenter observational clinical study sponsored by the Michael J. Fox Foundation for Parkinson’s Research and uses a combination of advanced imaging, biologics sampling, and behavioral assessments to identify biomarkers of Parkinson’s disease progression. The current study focused on neuropsychiatric and cognitive data from baseline through the first 24 months of follow up. Participants included 423 newly diagnosed, untreated Parkinson’s patients and 196 healthy controls at baseline as well as 281 PD patients at 6 months. Of these, 261 PD patients and 145 healthy controls were evaluated at 12 months, and 96 PD patients and 83 healthy controls were evaluated at 24 months. PD patients were allowed to begin dopamine therapy at any point after their baseline evaluation. “We hypothesized that neuropsychiatric symptoms would be common and stable in severity soon after diagnosis and that the initiation of dopamine replacement therapy would modify their natural progression in some way,” explained senior author Daniel Weintraub, MD, associate professor of psychiatry and neurology at the Perelman School of Medicine at the University of Pennsylvania in Philadelphia. Patients with PD experienced more depression, fatigue, apathy, and anxiety than healthy controls at every measurement period, according to the report, which added that both apathy and psychosis increased over time with Parkinson’s. Interestingly, the researchers also found that about two-thirds of PD patients who screened positive for depression at any clinic visit were not taking an antidepressant. At the 24-month visit, 44% of patients had been on dopamine replacement therapy for at least a year and reported more excessive daytime sleepiness and incident impulse control disorders such as compulsive gambling, sexual behavior, eating, or spending. Despite the adverse effects, dopamine therapy did help with fatigue, however, with 33% of patients improving their fatigue test score over 24 months versus 11% not on dopamine therapy. Noting that PPMI follows volunteers for 5 years, Weintraub said he considers the results preliminary. “We will more closely look at cognitive changes over time,” he said. “Two years is not a sufficient period of follow up to really look at meaningful cognitive decline.” The PPMI is a long-range study since many patients with the disease live for 10 to 20 years following diagnosis. “It's really a chance to assess the frequency and characteristics of psychiatric and cognitive symptoms in PD, compare it with healthy controls, and then also look at its evolution over time,” Weintraub noted. “The hope is that we will be able to continue this work so that we can obtain long-term follow up data on these patients.”
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