Cognitive impairment may be part of prodromal PD

By Eleanor McDermid, Senior medwireNews Reporter

Research shows that people with a theoretical high risk of developing Parkinson’s disease (PD) have significant cognitive deficits, particularly affecting executive function.

The findings emerge from an analysis of 225 participants of the Parkinson Associated Risk Syndrome (PARS) study who undertook a battery of cognitive tests.

Thirty-eight of these patients, who were thought to be at high risk of developing PD because they had both hyposmia and reduced dopamine transporter (DAT) binding, had significantly impaired cognition relative to the other participants, who had hyposmia only or neither risk factor.

Daniel Weintraub (Perelman School of Medicine at the University of Pennsylvania, Philadelphia, USA) and co-researchers note that the clinical relevance of their findings will become clear over time, as they are able to determine the rates of conversion to PD in the high-risk group versus the rest of the PARS participants.

“This will allow us to validate our techniques for identifying prodromal individuals and our predictive models for determining their future risk of PD”, they write in Movement Disorders.

Participants with hyposmia and reduced DAT binding had significantly reduced z scores for global cognition, executive function/working memory and memory, relative to the lower-risk participants. Scores for processing speed/attention, visuospatial function and language did not significantly differ between the groups.

However, after accounting for age, gender and years of education, worse processing speed/attention also became associated with high-risk status, at an odds ratio of 1.53. And worse global cognition, executive function/working memory and memory remained significantly associated with concurrent hyposmia and reduced DAT binding, at respective odds ratios of 1.97, 1.84 and 1.64.

“This suggests that cognitive abnormalities may be part of the prodromal PD syndrome”, says the team, noting that this is consistent with findings in untreated patients with early PD.

Having hyposmia was associated with a 4.14-fold increased odds of having reduced DAT binding, after accounting for age, gender and years of education, and adding reduced global cognition or executive function/working memory raised this further, to nearly a sevenfold increased odds.

The researchers observe, however, that these and other typical prodromal symptoms, such as constipation, are very nonspecific for PD, especially in older people, underlining the value of combining predictive symptoms.

“The results presented herein suggest the incorporation of cognitive performance into such models as well”, they conclude.

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