Megan Brooks

June 21, 2013

SYDNEY, Australia – Mild cognitive impairment (MCI) in patients with newly diagnosed Parkinson's disease (PD) is more common than previously reported, affecting roughly 40% of patients, a new study suggests.

"The most common cognitive domain affected is memory," Alison Yarnall, MRCP, from the Institute of Ageing and Health, Newcastle University, United Kingdom, who worked on the study, told Medscape Medical News.

She presented the study findings June 18 during the Movement Disorder Society (MDS) 17th International Congress of Parkinson's Disease and Movement Disorders. Her poster received the MDS Junior Award at the conference.

Increasing Attention

Dementia often complicates PD, with a cumulative incidence approaching 80% in community studies. MCI in PD may be a predementia state and has received "increasing attention recently," Dr. Yarnall said.

To better characterize MCI in incident PD, Dr. Yarnall and colleagues evaluated baseline data on cognitive function among participants in the Incidence of Cognitive Impairment in Cohorts with Longitudinal Evaluation (ICICLE-PD) study, which aims to determine predictors for dementia in PD.

Between June 2009 and December 2011, 219 participants with newly diagnosed PD and 99 age-matched controls underwent neurologic assessments, including tests of global cognition, attention, memory, executive function, visuospatial function, and language.

Using recently released diagnostic criteria for MCI in PD, participants were classified as level 1 MCI if they scored less than 26 on the Montreal Cognitive Assessment, a rapid screening instrument for MCI (total possible score of 30, with 26 or greater considered normal).

They were classified as level 2 MCI if they were impaired on 2 tests in 1 cognitive domain or had 1 impaired test in 2 different domains at 1, 1.5 or 2 standard deviations (SDs) below normative values.

They researchers found that 41.5% patients with PD met criteria for level 1 MCI (score < 26 on the Montreal Cognitive Assessment).

In addition, 65.8% of patients with PD met criteria for level 2 MCI at 1 SD below normative values, 42.5% at 1.5 SDs, and 22.4% at 2 SDs.

By contrast, a recent pooled analysis of data published in Neurology found MCI in 26% of patients with incident PD.

In Dr. Yarnall's study, memory impairment was the most common deficit in patients with PD (15.1%), followed by visuospatial (13.2%), attention (12.3%), and executive (11.0%) dysfunction.

"We speculate that PD patients with MCI might be at increased risk of future PD dementia," Dr. Yarnall told Medscape Medical News.

Indeed, a study published in JAMA Neurology in March found that MCI at diagnosis of PD predicts progression to dementia.

As reported by Medscape Medical News at that time, the study showed that more than 25% of patients who had MCI when PD was diagnosed developed dementia within 3 years compared with less than 1% of patients with newly diagnosed PD who did not have MCI.

"Cognitive testing should be performed in the early phase of PD, even at the time of PD diagnosis, to detect patients with MCI who need closer monitoring of cognitive status during follow-up," the study's lead author, Kenn Freddy Pedersen, MD, PhD, from the Norwegian Centre for Movement Disorders, Stavanger University Hospital, Norway, commented.

Dr. Yarnall agrees that early identification of PD-MCI is important. "Identifying those at high risk of future cognitive decline represents an opportunity for disease modification and early therapeutic interventions, when the viable neuronal population is greater," she said.

The study was funded by Parkinson's UK. The authors have disclosed no relevant financial relationships.

Movement Disorder Society (MDS) 17th International Congress of Parkinson's Disease and Movement Disorders. Abstract 505. Presented Tuesday June 18, 2013.


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