Should mild cognitive impairment be subtyped?

Purpose of review To review evidence on the validity and utility of recent approaches to subtyping late-life mild cognitive impairment. Recent findings There is growing evidence that amnestic mild cognitive impairment is associated with biomarkers for Alzheimer's disease, while nonamnestic mild cognitive impairment maps more closely to cerebrovascular disease. The former is more likely to progress to dementia than the latter. Mild impairment in multiple cognitive domains appears to represent a more advanced disease state than single-domain impairment, and is more likely to progress to dementia. The cognitive subtypes have imprecise boundaries and have limited ecological validity. Approaches to subtyping that also incorporate biomarkers increase diagnostic specificity and have greater predictive value. However, these approaches have yet to be validated outside specialized memory clinic populations. Summary Mild cognitive impairment as currently defined is still etiologically and prognostically heterogeneous, particularly outside specialty clinical settings. The objective of further subtyping is to delineate subgroups that are more clinically homogeneous. The current cognitive subtypes have some validity and utility but additional approaches should be explored so as to enhance these properties.