SYDNEY, AUSTRALIA – Patients with mild cognitive impairment in Parkinson’s disease often show memory impairment and problems with visuospatial function, attention, and executive function, according to a study attempting to characterize the condition.
A cohort study assessed 219 patients newly diagnosed with Parkinson’s disease but without dementia and 99 age-matched controls using new criteria for the diagnosis of mild cognitive impairment in Parkinson’s disease (PD-MCI).
Dr. Alison Yarnall
The criteria, released last year by the Movement Disorder Society, include tests of global cognition, attention, memory, executive function, visuospatial function, and language (Mov. Disord. 2012;27:349-56).
Patients were classified as having level 1 MCI if they scored less than 26 out of 30 on the Montreal Cognitive Assessment (MoCA), and as level 2 MCI if they were impaired on two tests in one cognitive domain or one impaired test in two different domains at 1, 1.5, or 2 standard deviations (SD) below normative values.
According to data presented in the Junior Award session at the international congress of Parkinson’s Disease and Movement Disorders, 41.5% of participants met the criteria for level 1 PD-MCI, while 65.8% met level 2 criteria at 1 SD below normative values, 42.5% at 1.5 SD, and 22.4% at 2 SD below norm.
The study found that among participants at 1.5 SD below normative values, memory impairment was the most common deficit (15.1%), followed by visuospatial (13.2%), attention (12.3%), and then executive dysfunction (11%).
Language function did not appear to be particularly affected, although lead author Dr. Alison Yarnall, clinical research fellow at the Institute for Ageing and Health at Newcastle University, Newcastle upon Tyne, England, said this may be because the tests weren’t sensitive enough to detect it.
"[The participants] also tended to be older. They had greater Parkinson’s disease severity even though it was still earlier on in the disease. They were more depressed, and they tended to be people [who] had reduced educational levels," Dr. Yarnall said in an interview.
Cerebrospinal fluid samples were also taken from some patients, and researchers found a significant correlation between amyloid-beta 42 levels, MoCA scores, and pattern recognition memory.
There were also significant differences in amyloid-beta 42 and 40 levels between patients who were cognitively normal and those who were impaired.
While the frequency of patients meeting the criteria for MCI was higher than had been shown in previous studies, Dr. Yarnall suggested this may be a factor of using the new criteria for diagnosis of PD-MCI.
"This is really the first step toward identifying patients with PD-MCI because, prior to last year, we didn’t have any of these standardized criteria and most of the other studies that are published in it extrapolated from the Alzheimer’s literature," Dr. Yarnall said.
While there are no treatments currently licensed for treatment of PD-MCI, Dr. Yarnall said identifying this cohort of individuals with PD-MCI could provide an opportunity for future research and treatment. Characterizing these patients could also help with identifying Parkinson’s disease patients at greater risk of developing dementia.
The research is part of the ongoing ICICLE-PD prospective cohort study that aims to determine predictors for dementia in Parkinson’s. It is funded by Parkinson’s UK and supported by the National Institute for Health Research. There were no other relevant conflicts of interest declared.