Longitudinal course and neuropathologic outcomes in original vs revised MCI and in pre-MCI
Martha Storandt1, Elizabeth A Grant, J Philip Miller
1Department of Psychology, Washington University, St. Louis, MO, USA.
Objectives:
To compare the natural history of individuals classified with mild cognitive impairment (MCI) in accordance with original criteria to the natural history of individuals classified with revised MCI criteria.
Methods:
The authors compared the rates of progression in 32 individuals with amnestic MCI and in 90 people with MCI according to revised criteria that allow nonamnestic deficits with progression in 276 individuals who were too minimally impaired (pre-MCI) to meet either MCI criteria. All individuals in this study were determined clinically to be very mildly cognitively impaired with a Clinical Dementia Rating (CDR) of 0.5.
Results:
Rates of progression for the two MCI groups were similar with a decline of almost 0.50 SD per year on a psychometric composite. Decline was less (0.23 SD) in the pre-MCI group. Median survival time to CDR 1 (mild dementia) was comparable for the original (95% CI: 3.79 to 4.07 years) and revised (95% CI: 3.29 to 5.40) criteria MCI groups but approximately twice as long in the pre-MCI group (95% CI: 6.72 to 8.93). All cases from the amnestic MCI criteria group with neuropathologic diagnoses met criteria for Alzheimer disease as did more than 90% in the other two groups.
Conclusions:
Mild cognitive impairment as originally and currently defined is usually early stage Alzheimer disease, which can begin with a cognitive deficit other than memory. It is possible to identify Alzheimer disease at an even earlier stage than mild cognitive impairment by focusing on intraindividual change rather than comparison with group norms.
Insights
Mild cognitive impairment (MCI) diagnosed by original or revised criteria shows similar progression rates, often indicating early Alzheimer's disease. Identifying cognitive decline earlier than MCI is possible by tracking individual changes.
Area of Science:
- Neurology
- Gerontology
- Cognitive Science
Background:
- Mild cognitive impairment (MCI) is a transitional stage between normal cognition and dementia.
- Diagnostic criteria for MCI have evolved, necessitating comparison of their prognostic value.
- Understanding the natural history of MCI is crucial for early intervention in neurodegenerative diseases.
Purpose of the Study:
- To compare the natural history of individuals diagnosed with mild cognitive impairment (MCI) using original versus revised diagnostic criteria.
- To assess the progression rates and time to mild dementia (CDR 1) in different cognitive impairment groups.
Main Methods:
- Retrospective analysis of 32 individuals with amnestic MCI and 90 with MCI (revised criteria) compared to 276 individuals with pre-MCI (Clinical Dementia Rating 0.5).
- Progression was measured by psychometric composite decline and time to reach CDR 1.
- Neuropathologic diagnoses were correlated with clinical classifications.
Main Results:
- Progression rates were similar for original and revised MCI criteria groups (approx. 0.50 SD/year decline).
- The pre-MCI group showed slower decline (0.23 SD/year).
- Median time to mild dementia was comparable for both MCI groups but significantly longer for the pre-MCI group.
Conclusions:
- Mild cognitive impairment, by both original and revised definitions, frequently represents early-stage Alzheimer's disease.
- Alzheimer's disease may manifest with non-amnestic cognitive deficits.
- Identifying Alzheimer's disease at even earlier stages than MCI is feasible by monitoring intraindividual cognitive changes.
