Predictors of independence in instrumental activities of daily living: Amnestic versus nonamnestic MCI.

Introduction: Individuals with mild cognitive impairment (MCI) demonstrate deficits in instrumental activities of daily living (IADL) that place them at high risk for progression to dementia. The cognitive profiles, IADL deficits, and risk of progression differ between MCI subgroups of amnestic (aMCI) and nonamnestic MCI (naMCI), though many studies of functional impairment have not examined these subgroups separately. This study aims to determine whether common neuropsychological measures, as well as the related concept of patient anosognosia, are associated with IADL functioning differently in aMCI compared to naMCI.

Method: Seventy-one individuals were identified as naMCI, and 99 individuals were identified as aMCI based on neuropsychological evaluation. Controlling for age, gender, and education, we examined whether performance on neuropsychological tests predicted informant-rated IADL dysfunction. We also investigated the ability of patient awareness, as rated by clinicians and informants, to predict informant-rated IADL dysfunction within MCI subgroups.

Results: Better performance in cognitive domains of attention/processing speed and executive functioning predicted IADL independence in aMCI, but not in naMCI. Exploratory analysis with a subset of these individuals revealed that after accounting for an estimate of cerebrovascular burden, better performance in Delayed Memory predicted IADL independence in the naMCI group, but not in the aMCI group. Lastly, informant, but not clinician, ratings of patient awareness predicted IADL independence within the aMCI group only.

Conclusion: Neuropsychological performance on tests of attention/processing speed and executive functioning may be better able to predict cognitive contributions to IADL dysfunction specifically in aMCI. After controlling for vascular burden, memory deficits may be the earliest cognitive indication of IADL dysfunction in naMCI. These results suggest that executive functions and memory, in addition to patient's awareness of deficits, differentially predict early IADL dysfunction in subgroups of MCI and can be used to formulate patient prognosis and recommendations on a more individualized basis.