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Predicting Dementia in Early Parkinsonís Disease

Doctors may be able to estimate which people with Parkinson’s disease are more likely to develop dementia by using assessment tools, say researchers in the March 25 issue of JAMA Neurology. Catching signs of cognitive impairment early may offer people a chance to halt the onset of dementia.

It is estimated that at any one time, one quarter to one third of people with Parkinson’s disease have symptoms of mild cognitive impairment (MCI). Generally, these changes are mild and will not interfere with a person’s ability to function. But researchers were not sure if, as happens in Alzheimer’s disease, this mild form of impairment was predictive of more severe dementia. Last March, the Movement Disorder Society Task Force developed a uniform list of criteria to help doctors detect mild cognitive impairment in people with PD1. It includes tests to measure attention span, verbal memory, spatial skills, and executive functions such as the ability to plan in advance. But the criteria had not yet been proven as useful for detecting MCI or predicting dementia in people with Parkinson’s. 

A research team led by Kenn Pedersen, M.D., Ph.D., at the Norwegian Center for Movement Disorders in Bergen put the MDS Task Force’s criteria to the test. As part of an ongoing study, Dr. Pedersen’s team followed 182 Norwegians who had recently been diagnosed with PD, did not have dementia, and were not yet on medication. Each person had been tested for the presence of mild cognitive impairment at the time of diagnosis. Dr. Pedersen and his colleagues then tested each participant again, during the first and third year of their study, using the new criteria.


  • Among the 37 people who experienced mild cognitive impairment at the time of their PD diagnosis, 27 percent (10 people) developed PD dementia by year three.
  • Among the 145 people without mild cognitive impairment at the time of their PD diagnosis, .7 percent (1 person) developed PD dementia by year three.
  • Among people who experienced mild cognitive impairment both at the time of their PD diagnosis and one year later, 45.5 percent (10 participants) were diagnosed with PD dementia at year three.
  • Among people who experienced mild cognitive impairment both at the time of their PD diagnosis and one year later, two no longer had impairment (or dementia) at year three.
  • People who were diagnosed with mild impairment at year one according to Task Force criteria, but who did not develop dementia at year three were significantly younger than those who acquired dementia (mean age 69.4 years compared with 74.9 years).

What Does It Mean?

One of the most serious concerns for people with PD is: will I develop dementia? Since a less serious form of cognitive impairment often precedes Alzheimer’s, researchers investigated the same phenomenon in PD.

They now report, in this study, that mild cognitive impairment can help to predict dementia in people with PD. They found that the accuracy of this prediction improved when a person tested positive for mild cognitive impairment repeatedly.

In converse, this study indicates that people with PD who are not diagnosed with mild cognitive impairment may rest assured that they are unlikely to develop dementia within the next three years.

Because the authors focused on a relatively small group of white people with PD in Norway, the team’s results may not hold true across the board. Cognitive issues are known to vary according to age, education level, socioeconomic status and other factors. Still, the study points out the potential of the Movement Disorder Society Task Force criteria, and the authors recommend both its widespread adoption by doctors and larger studies to further assess its merit.

Diagnosing cognitive impairment requires careful evaluation, using clinical tools to find out how cognitive function affects daily life, and formal neuropsychological testing (similar to IQ tests). Researchers are seeking interventions to stall the onset of dementia and so far, studies indicate that therapies work best when initiated early.

Therefore, a test for PD mild cognitive impairment may soon help people with PD to identify potential risks and, cope with possible changes.

Learn More

Do you have more questions about cognition and Parkinson's?  Contact PDF's HelpLine at (800) 457-6676 or, or use our free resources below.

View PD ExpertBriefing: Cognition and Parkinson's: What You've Always Wanted to Know But Were Too Afraid to Ask
Download Fact Sheet: Cognitive Changes in PD

Reference: Pedersen KF, Larsen JP, Tysnes O-B, Alves G (2013) Prognosis of Mild Cognitive Impairment in Early Parkinson Disease: The Norwegian ParkWest Study. JAMA Neurol:1–7. Ahead of Print. doi:10.1001/jamaneurol.2013.2110

1 Litvan, I. et al. (2012) Movement Disorders 27(3): 349-56.

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Source Date: Apr 19 2013