Parkinson's Decline Comes Sooner than Thought

Cognitive decline may occur faster than previously shown in patients with Parkinson’s disease, especially those with certain predictive characteristics, a new study shows.

“The results from this prospective study in a well-characterized cohort indicate a high risk of developing new-onset cognitive impairment, including dementia, in patients with well-established [Parkinson’s Disease]. Within this group, men and those with more severe motor disease and even subtle decreases in cognitive abilities… are at greatest risk of future cognitive decline,” lead author Kara Pigott and team wrote in a report published online on September 11 in Neurology.

The researchers from the Perelman School of Medicine at the University of Pennsylvania in Philadephia found that cognitive impairment affects nearly half of patients within five years of baseline and in those who have mild cognitive impairment, all patients progressed to dementia within six years.

Cognitive impairment is a significant risk for people with Parkinson’s disease, with severe consequences for both patients and caregivers. Studies have shown that 80 percent of patients eventually develop dementia. However, few studies have measured how quickly cognitive impairment sets in or what the risk factors are. Since structural MRI, and plasma and CSF biomarkers associated with cognitive decline are invasive and costly, and can only be tested at academic centers, identifying other predictive factors may be useful in assessing risk of progressing to dementia.

Pigott’s group set out to identify key predictors of progression from normal cognition to cognitive impairment and dementia in a prospective study of Parkinson’s disease patients. They followed 141 patients with Parkinson’s disease but no evidence of cognitive impairment for up to six years between 2006 and 2012. All participants underwent annual or biannual neuropsychological testing and were enrolled in the study at the National Institute of Neurological Disorders and Stroke.

“We demonstrated that cognitive impairment, including dementia, develops commonly and relatively quickly in patients with established [Parkinson’s disease] with normal cognition.

“The importance of recognizing dementia at an early stage in patients with [Parkinson’s disease] is that cholinesterase inhibitors such as rivastigmine have been shown in randomized clinical trials to be effective in promoting cognitive function and in reducing global impairment that is associated with this disease,” wrote Linda A. Hershey, MD, PhD, and Guerry, M. Peavy, PhD, and an accompanying editorial. “In addition, strong evidence of early cognitive decline in [Parkinson’s disease] 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.”