Cognitive Profiles and Subtypes of Patients with Mild Cognitive Impairment: Data from a Clinical Follow-Up Study

Abstract

Background: Mild cognitive impairment (MCI) is a heterogeneous condition with a variety of clinical outcomes, the presence of which correlates with risk of Alzheimer’s disease as well as pre-clinical stages of other dementia subtypes. The aims of this study were to assess the specific patterns of cognitive profiles and to identify changes from baseline to 24 weeks in patients with MCI using detailed neuropsychological testing. Methods: We consecutively recruited 120 MCI patients at baseline according to the Petersen’s clinical diagnostic criteria, who were admitted to the Dementia and Memory Clinics. We analyzed patients who fulfilled both inclusion and exclusion criteria for MCI and classified them into four subtypes according to deficits in major cognitive domains; amnestic MCI single domain (aMCI-s), amnestic multiple domain MCI (aMCI-m), non-amnestic single domain MCI (naMCI-s) and non-amnestic multiple domain MCI (naMCI-m). Four groups of MCI were evaluated by a detailed neuropsychological battery test. Results: 83 patients with MCI at the 24-week follow-up were classified into four subtypes. The most frequent subtype was amnestic multi-domain MCI, with the frequency of MCI subtypes as follows: aMCI-s (n = 21, 25.3%), aMCI-m (n = 53, 63.9%), naMCI-s (n = 5, 6.0%) and naMCI-m (n = 4, 4.8%). In the major cognitive items of the SNSB-D, there were significant changes between the initial and follow-up tests in the domains of language, memory and the fron-tal/executive function (p < 0.05), except for attention, in all MCI patient subtypes. At 24-weeks follow-up, the conversion rate to Alzheimer’s disease was 2.4% (n = 2) from a subtype of amnestic multi-domain MCI. Conclusions: Our study revealed the most frequent subtype of MCI to be multiple domain amnestic MCI, with this subtype having a higher tendency of conversion to Alzheimer’s disease.