Paris, France—Impulse-control disorders (ICDs) might be more common than pharmacists or other healthcare professionals assume in patients on certain treatments for Parkinson’s disease, according to a new study.

The article in the journal Neurology suggests that half of those patients might develop uncontrolled gambling, shopping, eating or other compulsions. The issue, note French researchers, is related to how drugs such as dopamine agonists (DA) work in the brain.

“Our study suggests that impulse control disorders are even more common than we thought in people who take dopamine agonists,” explained study author Jean-Christophe Corvol, MD, of the ICM Brain and Spine Institute–Pitié-Salpêtrière Hospital, Assistance Publique–Hôpitaux de Paris, Sorbonne University. “These disorders can lead to serious financial, legal and social and psychological problems.”

For the study, researchers focused on 411 patients who had been diagnosed with Parkinson’s disease for 5 years or less. Over an average of 3 years of follow-up, the participants were questioned in interviews about ICDs such as compulsive shopping, eating, gambling or sexual behaviors.

Most of the participants, 87%, had used a DA at least once, and 20% of respondents reported an ICD. Those included:
• 11% had compulsive- or binge-eating problems 
• 9% compulsive sexual behaviors
• 5% compulsive shopping, and 
• 4% compulsive gambling 

Overall, 6% had more than one ICD.

Study results indicate that, of the 306 patients who did not have ICDs at study initiation, however, 94 developed at least one during the study, for an overall 5-year cumulative incidence of 46%. 

Researchers report that the 5-year cumulative incidence of ICDs was 51.5% for DA ever-users 95% CI 41.8–62.1] versus 12.4% for DA never-users [95% CI 4.8–30.0]). Over 5 years, they write, ICD prevalence increased from 19.7% at baseline to 32.8%, adding that ICDs were associated with ever-DA use (prevalence ratio 4.23, 95% CI 1.78–10.09). 

“Lifetime average daily dose and duration of treatment were independently associated with ICDs with significant dose-effect relationships,” the article notes. “Similar analyses for levodopa were not in favor of a strong association. ICDs progressively resolved after DA discontinuation.”

The study authors add, “ICDs were strongly associated with DA use with a dose-effect relationship; both increasing duration and dose were associated with ICDs. ICDs progressively resolved after DA discontinuation.” Pramipexole and ropinirole were associated with the highest risk of developing the disorders, they advise.

“These disorders can be challenging for neurologists to discover,” noted Laura S. Boylan, MD, of New York University, who wrote an editorial accompanying the article. “People might be ashamed to tell their doctor about their problems, they may think these issues are not related to their Parkinson’s disease, or they may not even consider the disorders a problem. Plus, as doctors’ time for meeting with each patient gets shorter and shorter, bringing up sensitive issues gets harder and harder.”

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