The original mild cognitive impairment (MCI) criteria exclude substantial functional deficits, but recent reports suggest otherwise. Identifying the extent, severity, type, and correlates of functional deficits that occur in MCI and mild Alzheimer disease (AD) can aid in early detection of incipient dementia and can identify potential mechanistic pathways to disrupted instrumental activities of daily living (IADLs).
To examine the number, type, and severity of functional impairments and to identify the clinical characteristics associated with functional impairment across patients with amnestic MCI (aMCI) and those with mild AD.
Study using baseline data from the Alzheimer's Disease Neuroimaging Initiative.
Multiple research sites in the United States and Canada.
Samples included 229 control individuals, 394 patients with aMCI, and 193 patients with AD.
Main Outcome Measure
The 10-item Pfeffer Functional Activities Questionnaire (FAQ) assessed function.
Informant-reported FAQ deficits were common in patients with aMCI (72.3%) and AD (97.4%) but were rarely self-reported by controls (7.9%). The average severity per FAQ deficit did not differ between patients with aMCI and controls; both were less impaired than patients with AD (P < .001). Two FAQ items (remembering appointments, family occasions, holidays, and medications and assembling tax records, business affairs, or other papers) were specific (specificity estimate, 0.95) in differentiating the control group from the combined aMCI and AD groups (only 34.0% of patients with aMCI and 3.6% of patients with AD had no difficulty with these 2 items). The severity of FAQ deficits in the combined aMCI and AD group was associated with worse Trail Making Test, part A scores and smaller hippocampal volumes (P < .001 for both). Within the aMCI group, functionally intact individuals had greater hippocampal volumes and better Auditory Verbal Learning Test 30-minute delay and Trail Making Test, part A (P < .001 for each) scores compared with individuals with moderate or severe FAQ deficits. Patients with a high number of deficits were more likely to express the apolipoprotein ε4 allele (63.8%) compared with patients with no (46.8%) or few (48.4%) functional deficits.
Mild IADL deficits are common in individuals with aMCI and should be incorporated into MCI criteria. Two IADLs—remembering appointments, family occasions, holidays, and medications and assembling tax records, business affairs, or other papers—appear to be characteristic of clinically significant cognitive impairment. In patients with aMCI, impairment in memory and processing speed and greater medial temporal atrophy were associated with greater IADL deficits.