Impulse control disorders do not promote cognitive decline in PD

By Lucy Piper, Senior medwireNews Reporter

Impulse control disorders (ICDs) in patients with Parkinson’s disease (PD) are not associated with more marked impairment of cognitive function, researchers report.

Rather, they found that cognitive decline in patients with these disorders was relatively slower than that in PD patients without ICDs, and suggest that “ICDs might result from a medication-induced overstimulation of relatively preserved cognitive functions.”

At the start of the study, the 40 PD patients with ICDs, such as pathological gambling, binge eating and compulsions, and the 40 without scored comparably on measures of cognitive function. The only exception was slightly better semantic fluency in patients with ICDs.

Over a mean of 3.5 years of follow-up, the two groups of patients differed significantly in the degree to which cognitive dysfunction progressed. Patients with ICDs showed significantly less decline than those without in scores on the Frontal Assessment Battery, the Raven’s Coloured Progressive Matrices, attentive matrices and digit span tests, which are related to frontal lobe abilities, working memory and verbal short-term memory.

Remission of ICD was seen in 40% of affected patients, while partial remission (milder symptoms) was recorded in 25%. The two groups of remitters had similar PD-related features and therapy management strategies, including the extent of dopamine agonist dose reduction, as non-remitters.

They did differ, however, in their baseline performance on working memory-related tasks. Although mean testing scores were within the normal range for all the ICD patients, those with remitted ICDs scored consistently and significantly better than non-remitters on the digit span test, the Rey Auditory Verbal Learning Test (RAVLT) immediate, RAVLT recall and attentive matrices.

Indeed, multivariate logistic regression models showed that digit span and attentive matrices, which together represent verbal working memory performance, were independently associated with ICD remission, at odds ratios of 2.69 and 1.19, respectively.

“Taken as a whole, these observations suggest that ICD patients with better functioning of higher-level abilities (ie, working memory) might have more cognitive resources to develop effective strategies to cope with the abnormal behaviors and thus increase their chances of long-term remission”, observe Roberto Cilia (Istituti Clinici di Perfezionamento, Milan, Italy) and colleagues.

They conclude in Movement Disorders: “Cognitive training focused on working memory skills may be associated with pharmacological optimization in patients with ICDs to increase their chances of sustained remission.”

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