Researchers report that nearly half of patients with Parkinson’s disease (PD) develop cognitive impairment within about a decade, and progress rapidly to dementia.
The 141 patients in the study had normal cognition at baseline and an average disease duration of 5.0 years. After 6 years of follow-up, the estimated cumulative rate of any cognitive impairment was 47.4%, with a mild cognitive impairment (MCI) rate of 43.0%.
And all patients diagnosed with MCI during the course of the study progressed to dementia within the next 5 years.
“These findings are in contrast to those reported for MCI in the general population, in which the majority of patients will not progress to dementia even after 10 years of follow-up”, say Daniel Weintraub (Perelman School of Medicine at the University of Pennsylvania, Philadelphia, USA) and study co-authors.
It indicates “that new-onset cognitive impairment in well-established PD represents prodromal dementia”, they add in Neurology.
After accounting for confounders, the team found that male gender, more severe motor symptoms and poorer baseline cognition predicted later cognitive impairment.
Weintraub et al used a battery of neuropsychological tests for the baseline assessments. Further analysis of these showed that patients’ performance on Letter-Number Sequencing, phonemic verbal fluency, animal naming, the short Boston Naming Test, and the Hopkins Verbal Learning Test–Revised total recall and recognition discrimination were the best predictors of later cognitive impairment.
However, editorialists Linda Hershey (University of Oklahoma Health Sciences Center, Oklahoma City, USA) and Guerry Peavy (University of California, San Diego, USA) note that baseline global cognitive performance on the Dementia Rating Scale–2 also predicted cognitive decline.
“This may be particularly helpful in settings in which comprehensive cognitive evaluations and lengthy problem-solving discussions are not possible”, they say.
Hershey and Peavy highlight the importance of early recognition of cognitive decline, when it is potentially amenable to pharmacological intervention.
“In addition, strong evidence of early cognitive decline in PD underscores the importance of acknowledging and accurately labeling deficits in order to guide patients and caregivers with respect to their expectations and their ability to develop strategies to improve daily functioning.”
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