Chicago, Illinois - June 26, 2008 — A new study performed in 3090 patients with Parkinson's disease found a 2- to 3-fold increased risk of having an impulse control disorder among patients treated with dopamine agonists compared with those who did not receive dopaminergic therapy.
The multicenter cross-sectional study examined in Parkinson's disease patients the prevalence of 4 impulse control disorders: problem or pathologic gambling, compulsive buying, compulsive sexual behavior, and binge eating.
The results were presented here at the 12th International Congress of Parkinson’s Disease and Movement Disorders.
Lead author Daniel Weintraub, assistant professor of psychiatry at the University of Pennsylvania stated: "It is the largest study showing an association [between impulse control disorders and Parkinson's disease medications] and the only one to study all 4 of these disorders."
Dr. Weintraub went on to say that impulse control disorders appear to be common in patients with Parkinson's disease receiving dopamine agonists. Their study showed that 13.6% of all treated patients had at least 1 such disorder (17.1% in patients receiving dopamine agonists). Of the patients with an impulse control disorder, 36% had more than 1 of these disorders.
Case reporting and preliminary cross-sectional studies have previously suggested an association between dopamine agonist therapy and impulse control disorders, they write. However, to date, the studies have typically used "convenience" samples, had relatively small samples sizes, and have not concurrently assessed all of the impulse control disorders that have been reported to date with these medications.
The study population for this report included a total of 3090 Parkinson’s disease patients, recruited for participation in the context of routine clinical care from 46 movement disorders centers in the United States and Canada. Overall, 86.8% of patients were receiving levodopa, according to the abstract. Two thirds of the patients were receiving treatment with 1 or more dopamine agonists, and most of those also were taking levodopa.
Impulse control disorders were diagnosed using a modified Massachusetts Gambling Screen for problem or pathologic gambling, a modified Minnesota Impulsive Disorders Interview for compulsive sexual behavior and buying, and the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, research criteria for binge-eating disorder.
The most common impulse control disorder found was compulsive buying (7.2%), they report. More than 6% of patients had problem or pathologic gambling, 5.6% had binge-eating disorder, and 4.4% experienced compulsive sexual behavior.
Logistic regression analysis found that both dopamine agonist therapy and levodopa treatment were associated independently with a higher risk for an impulse control disorder, as was a higher dose of either type of medication. Duration of treatment was not analyzed in these preliminary data, according to Dr. Weintraub.
"The strongest factor that contributed to a higher frequency of impulse control disorders was dopamine agonist treatment," he said in an interview. The frequency was similar for all dopamine agonists that patients reported using, including pramipexole, ropinirole, and pergolide, suggesting a class effect.
Other variables that were independently associated with a higher risk of having an impulse control disorder were younger age (65 years or younger), single marital status, and a family history of gambling problems, the authors reported. Multiple factors, therefore, may contribute to the development of impulse control disorders in patients with Parkinson's disease, the authors concluded.
The study results may have implications for clinical practice. Dr. Weintraub explained that: "There is a role for a careful medical history pertaining to impulse control disorders in Parkinson's disease patients, especially those receiving dopamine therapy and perhaps even levodopa."
The chair of the Congress Scientific Program Committee, Serge Przedborski, MD, PhD, said that despite the study showing association rather than proving causation, it provides useful information for physicians who treat Parkinson’s disease.
"The study brings an interesting take-home message for the practitioner," said Dr. Przedborski, professor of neurology and pathology at Columbia University in New York City. "We should add impulse control disorders to the list of warnings to inform patients when prescribing treatment."
It also may be necessary to lower the dose or otherwise adjust treatment if a patient with Parkinson’s disease has a family history of impulse control disorders, he said.