Parkinson’s disease, essential tremor impair cognitive performance
Both Parkinson’s disease (PD) and essential tremor (ET) negatively influence cognitive performance even in the absence of dementia, with PD showing a greater effect than ET, according to a study. Furthermore, while the deficits are in many of the same cognitive domains, the affected domains do not completely overlap.
The study used data from the NEDICES study involving 2,438 individuals without dementia who went through a short neuropsychological battery test. Nonparametric techniques were applied to assess for differences in and/or a gradient of impairment across the three patient groups: PD (n=46), ET (n=180) and healthy controls (n=2,212). A head-to-head comparison of cognitive performance in PD and ET were also performed, with adjustments made for the confounding effects of age and education.
Compared with controls, PD and ET patients had poorer cognition. There was a notable gradient of performance impairment, such that the PD group performed poorly than the ET group and then each of these groups performed worse than controls. This gradient was observed in memory (p<0.05) and verbal fluency (p<0.001) tasks.
When the PD and ET groups were compared, the former had poorer scores in verbal fluency (p<0.05), whereas the latter had a poorer cognitive processing speed (p<0.05).
The present data have the potential to add value to the differential diagnosis, prognosis and management of movement disorders, researchers said.
Patients with PD and ET are at a greater risk of cognitive impairment compared with age- and education-matched healthy individuals. Both conditions show a pattern of dysfunction labelled as that of a fronto-subcortical type, with deficits in domains including attention, verbal fluency and memory being seen at early stages. Cognitive impairment has been associated with degeneration of cortical association areas in PD, whereas the neuropathological correlates of impairment in ET have not been completely elucidated. [J Neurol Sci 2011;310:176–182; Mov Disord 2014;29:694–703; Neurology 2013;81:60–66; Parkinsonism Relat Disord 2014;20:655–658]