Mild cognitive impairment and on to dementia

In this issue of Neurology®, a study from the Chicago Health and Aging Project shows that persons with dementia of the Alzheimer type (DAT) decline more rapidly than persons with mild cognitive impairment (MCI), and that patients with MCI decline more rapidly than cognitively normal persons.¹ The findings have important implications for understanding the relationships between the clinical manifestations and the pathology of Alzheimer disease (AD).

In longitudinal studies, there is an acceleration of decline in cognition preceding the diagnosis of dementia.^2,3 The observations of Wilson et al.¹ on the differences between normal cognition and MCI are consistent with these prior observations. The finding of acceleration of decline between MCI and DAT has not been previously established in persons with incident cognitive impairment. Clinical trial experience in MCI and DAT certainly shows differences in rates of progression between the 2 groups. Patient groups with prevalent MCI or DAT are more likely to include some persons with static conditions. In contrast, incident cases are those persons who, by definition, are exhibiting recently recognized decline. By studying incident cases of MCI, Wilson et al. have a reasonable assurance that they have identified persons with MCI who have a progressive condition. In addition, the Chicago Health …