ISTANBUL, TURKEY — The first-ever brief screening questionnaire for impulse-control disorders in patients with Parkinson's disease is now available.
The self-administered Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease (QUIP) takes but several minutes for patients to complete. QUIP is the product of a collaboration between many of the leading investigators in the field of impulse-control disorders (ICDs) in Parkinson's disease, who recognized that it's impractical for busy office-based practitioners to find time to conduct lengthy diagnostic interviews with all of their patients who have Parkinson's, Dr. Daniel Weintraub explained at the annual congress of the European College of Neuropsychopharmacology.
The need for a brief screening instrument was highlighted in a landmark cross-sectional study led by Dr. Weintraub, which demonstrated that ICDs are relatively common in the setting of Parkinson's disease, being present in one in six patients.
Fourteen percent of the 3,090 Parkinson's disease patients under age 75 surveyed at 46 U.S. and Canadian movement disorder centers had at least one of the four major ICDs, involving pathological gambling, compulsive buying, binge-eating behaviors, and compulsive sexual behavior. Comorbidity was common: Among patients with an ICD, 36% had more than one, added Dr. Weintraub, a psychiatrist at the University of Pennsylvania, Philadelphia.
Although ICD is the generally accepted term for these behaviors, they have also been referred to as appetitive behaviors or behavioral addictions. These are not life-long behaviors in affected individuals; rather, they are changes that emerge during the course of Parkinson's disease and cause significant and often enduring distress or impairment.
“These ICDs are not pleasurable activities anymore, but something they feel they need to do,” Dr. Weintraub explained.
Pathological gambling was the first ICD to be described in those with Parkinson's disease when the association was initially recognized half a dozen years ago, but in fact all four ICDs were roughly equally prevalent in the North American survey.
In a multivariate analysis, by far the strongest correlate or risk factor for ICDs was being on dopamine-agonist therapy, which carried a 2.7-fold increased risk. Indeed, the population-attributable risk of dopamine-agonist treatment was 49%, meaning nearly half of all ICDs could be attributed to the drug therapy. The ICD risk was not affected by the specific agent prescribed, nor was it dose-dependent.
Other independent correlates with ICDs included current smoking, age 65 or younger, levodopa therapy, being unmarried, and living in the United States. Specifically, Americans had higher rates of compulsive buying and gambling, which Dr. Weintraub attributes to the prevailing social/cultural milieu.
A family history of gambling problems was associated with increased rates of all of the ICDs except sexual behaviors. There was no gender difference in the overall rate of ICDs; however, compulsive sexual behaviors were vastly more common among men, and binge-eating behaviors and compulsive buying were significantly more common in women.
Physicians can gain access to the QUIP screening tool via its recently published validation study (Mov. Disord. 2009;24:1461-7), which showed that a shortened version—the QUIP-S—containing 13 yes/no questions had a 94% sensitivity for detection of ICDs, nearly equal to that of the full 30-question version.
As a screening tool the emphasis in QUIP is on maximizing sensitivity at the expense of specificity. A positive result warrants a follow-up clinical interview to confirm the patient actually has an ICD, Dr. Weintraub stressed.
Physicians have an obligation to make their patients with Parkinson's disease aware that ICDs are a potential side effect of dopamine agonist therapy, and to monitor them for the emergence of these complications as part of routine clinical care. The same goes for psychiatrists who are exploring the use of these drugs for treatment of depression. The QUIP is intended to assist in that routine monitoring, he said.
He added that QUIP also might end up having a role in screening patients with disorders other than Parkinson's disease who are exposed to dopaminergic therapy. Dopamine agonists are now first-line therapy for restless legs syndrome, and although the doses used are generally considerably lower than in Parkinson's, some emerging evidence suggests that treated RLS patients may also have an increased prevalence of ICDs (Parkinsonism Relat. Disord. 2008;14:28-32).
Dopamine agonists are also seeing increasing use in patients with fibromyalgia.
The four major ICDs are listed under different diagnostic categories in DSM-IV. As a psychiatrist, it's fascinating to consider that the dopaminergic system links such diverse behaviors, Dr. Weintraub observed.
The North American survey of Parkinson's disease patients was funded by Boehringer Ingelheim, which supplied Dr. Weintraub with grant support and consulting fees.
