The validity of amnestic MCI and non-amnestic MCI at age 75 in the prediction of Alzheimer's dementia and vascular dementia.

BACKGROUND: Clinical subtypes of mild cognitive impairment (MCI) were assigned as potential prodromes to various types of dementia. Amnestic MCI (aMCI) is said to have a high likelihood of progressing to Alzheimer's dementia (AD) and non-amnestic MCI (naMCI) subtypes are assumed to have a higher likelihood of progressing to non-AD dementia. The aim of this study was to investigate the prognostic accuracy of aMCI and naMCI for the development of AD, vascular dementia (VaD), and mixed dementia.

METHODS: In this longitudinal study, 487 subjects without dementia (cognitively healthy: n = 387; MCI cases: n = 115) aged 75 years at baseline, who participated in a population-based cohort study (Vienna Transdanube Aging study), were available for analysis. The observation period was 90 months. The diagnoses of the clinical MCI subtypes were made according to common criteria. The outcome (AD, VaD, mixed dementia) was described for both MCI subtypes. Diagnostic values of aMCI and naMCI according to incident AD, VaD, and mixed dementia were determined.

RESULTS: AD was the most common type of dementia following both MCI subtypes. Participants with aMCI were more likely to progress to AD than participants with naMCI. The proportion of incident VaD and mixed dementia did not differ concerning the MCI subtypes. The positive predictive value for both MCI subtypes was low (range: 1%-46%), whereas the negative predictive value was high (range: 86%-99%).

CONCLUSIONS: The increased risk of clinical MCI subtypes for a particular type of dementia could only be confirmed for aMCI and incident AD.