Reversion From Mild Cognitive Impairment to Normal Cognition: A Meta-Analysis.

The initiation of Alzheimer disease (AD) prevention studies has placed greater emphasis on the need to accurately detect individuals with amnestic mild cognitive impairment (aMCI) given their increased risk for developing AD. Several studies reporting on the incidence and prevalence of aMCI have also found that a substantial number of aMCI cases at baseline assessments revert to normal cognition at subsequent assessments. This instability presents a major challenge to intervention studies aimed at preventing the onset of clinical symptoms associated with aMCI. Reversion rates from 25 studies were used for this meta-analysis which found an overall reversion rate of approximately 24%. When the studies were separated by their setting (community vs. clinic), substantial differences in reversion rates were noted with clinic-based studies having a much lower reversion rate (14%) than community-based studies (31%). North American and European studies had high heterogeneity of reversion rates, whereas Asian studies had moderate levels of heterogeneity and significantly lower rates of reversion. Continued improvement in diagnostic and classification methodologies may help in more accurately identifying aMCI cases which are less likely to revert to normal cognition.