MAY 11, 2017
Summary: Study reveals 46.5% of people who were diagnosed with MCI later tested as ‘normal’ during a follow-up assessment.
Source: University of New South Wales.
MCI is associated with a higher risk of dementia and for some people is an intermediate stage between normal cognitive ageing and dementia. NeuroscienceNews.com image is adapted from the UNSW news release.
Closer examination of Mild Cognitive Impairment (MCI) is critical in identifying individuals at high risk of developing dementia, new research finds.
Researchers looking at the trajectory of Mild Cognitive Impairment (MCI) say examining specific subtypes is critical in identifying individuals at high risk of developing dementia.
MCI is defined as having noticed cognitive decline which is confirmed by objective tests in people who are functioning well.
MCI is associated with a higher risk of dementia and for some people is an intermediate stage between normal cognitive ageing and dementia.
But there are many reasons why a person’s cognition might have declined such as depression, infection or reaction to medications.
So, it is not surprising that many individuals with MCI “revert” to normal cognition. What is less well known is that people who revert to normal from MCI have an increased risk of re-transitioning to MCI or progressing to dementia.
Dr Liesbeth Aerts of the Dementia Collaborative Research Centre at UNSW says the relevance of reversion for progression risk depends on the MCI subtype.
In a paper published in the journal Neurology, four biennial assessments of 705 elderly people in the UNSW Centre for Healthy Brain Ageing Sydney Memory and Ageing Study showed reversion from MCI was common.
Almost half of the people who had MCI at the start of the study (46.5%) tested as “normal” at least once during follow-up assessment.
But risk of progression to dementia was only lower for those who reverted from amnestic MCI, a subtype of MCI in which memory is affected.
Dr Aerts, the paper’s lead author, says it highlights the importance of subtype specificity.
“We need to be mapping these cognitive problems much better, because just saying ‘MCI’ is not enough to really know about dementia risk,” she says.
Longitudinal follow-up is crucial to determining which individuals with MCI are at high risk of developing dementia.
“In our study people’s performance on cognitive tests fluctuated or zig-zagged over time,” Dr Aerts says.
“Our results highlight that we need better assessment over time. Snapshot assessments should be considered in a larger perspective.
“Before, no one was thinking of reversion, we were only trying to capture people on decline.”
A bigger picture issue is the limitations of the cognitive tests, and the important role that biomarkers (biological indicators of dementia, for example changes in brain chemicals and imaging) will play in the future.
Changes in the brain occur long before the first symptoms become apparent, so being able to measure those will be crucial to identify people in the earliest stages of dementia.
“Researchers are shifting the frame to studying to what happens long before the onset of dementia in the hope of stopping the degenerative process in the brain in its tracks before dementia takes hold.”
Source: Gabrielle Dunlevy – University of New South Wales
Image Source: NeuroscienceNews.com image is adapted from the UNSW news release.
Image Source: NeuroscienceNews.com image is adapted from the UNSW news release.
Original Research: Abstract for “Effects of MCI subtype and reversion on progression to dementia in a community sample” by Liesbeth Aerts, Megan Heffernan, Nicole A. Kochan, John D. Crawford, Brian Draper, Julian N. Trollor, Perminder S. Sachdev, and Henry Brodaty in Psychological Science. Published online May 10 2017 doi:10.1212/WNL.0000000000004015
Abstract
Effects of MCI subtype and reversion on progression to dementia in a community sample
Objective: We sought to understand the trajectory of mild cognitive impairment (MCI) better by examining longitudinally different MCI subtypes and progression to dementia and reversion to normal cognition in a community sample.
Methods: We evaluated the stability of MCI subtypes and risk of dementia over 4 biennial assessments as part of an ongoing prospective cohort study, the Sydney Memory and Ageing Study.
Results: While prevalence of MCI and different MCI subtypes remains relatively stable across all assessments, reversion from MCI and transitions between different MCI subtypes were common. Up to 46.5% of participants classified with MCI at baseline reverted at some point during follow-up. The majority (83.8%) of participants with incident dementia were diagnosed with MCI 2 years prior to their dementia diagnosis. Both reverters and participants with stable MCI were at an increased risk of progression to dementia compared to those without MCI at baseline (HR 6.4, p = 0.02, and HR 24.7, p < 0.001, respectively); however, the risk of dementia in participants with MCI who did not revert was higher than in reverters (HR 2.5, p = 0.01). This effect was specific to amnestic subtypes (MCI reverters vs nonreverters: amnestic MCI HR 3.3, p = 0.006; nonamnestic MCI: HR 1.3, p = 0.67).Conclusion: Our findings indicate that the relevance of reversion for progression risk depends on the MCI subtype. Subtype specificity and longitudinal characterization are required for the reliable identification of individuals at high risk of developing dementia.
“Effects of MCI subtype and reversion on progression to dementia in a community sample” by Liesbeth Aerts, Megan Heffernan, Nicole A. Kochan, John D. Crawford, Brian Draper, Julian N. Trollor, Perminder S. Sachdev, and Henry Brodaty in Psychological Science. Published online May 10 2017 doi:10.1212/WNL.0000000000004015
http://neurosciencenews.com/mci-dementia-risk-6652/
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