Functional impairment as a defining feature of: amnestic MCI cognitive, emotional, and demographic correlates

Background: Early definitions of mild cognitive impairment (MCI) excluded the presence of functional impairment, with preservation of a person's ability to perform activities of daily living (ADL) as a diagnostic criterion. However, recent studies have reported varying degrees of functional impairment associated with MCI. Hence, we aimed to test the potential functional impairment associated with MCI and its predictors. Methods: Sixty-nine healthy elderly subjects, 115 amnestic single-domain MCI subjects (a-MCI), and 111 amnestic multi-domain MCI subjects (md-MCI) were assessed using a battery of neuropsychological tests including measures of attention, memory, working memory, executive functions, language, and depression. Additionally, functional ability was assessed by both qualitative (WHO-DAS II) and quantitative (CHART) instruments. Cognitive and functional performance was compared between groups, and regression analyses were performed to identify predictors of functional ability. Results: The md-MCI group was more impaired than the a-MCI group, and both were more impaired than healthy subjects in all cognitive measures, in total CHART score, CHART cognitive and mobility subscores, and WHO-DAS II communication and participation subscales. For the rest of the functional measures, the md-MCI group was more impaired than healthy controls. Prediction of functional ability by cognitive measures was limited to md-MCI subjects and was higher for the CHART than for the WHO-DAS II. The WHO-DAS II was largely influenced by depressive symptoms. Conclusions: Functional impairment is a defining feature of MCI and is partially dependent on the degree of cognitive impairment. Quantitative measures of functional ability seem more sensitive to functional impairment in MCI than qualitative measures, which seem to be more related to depression.