Neuropsychiatric symptom profiles in Mild Cognitive Impairment and Alzheimer's disease

Abstract

Mild cognitive impairment (MCI) is a risk state for Alzheimer's disease (AD). It has been well established that behavioral symptoms are commonly observed in AD. Our objective was to determine if the profile of neuropsychiatric symptoms in MCI was qualitatively unique to the profile found in AD. The data were obtained from the Alzheimer's Disease Neuroimaging Initiative (ADNI), a longitudinal study on healthy aging, MCI, and AD. These analyses included 393 individuals with MCI and 191 individuals with AD who all completed the Neuropsychiatric Inventory Questionnaire (NPI-Q), an informant-based rating scale for assessing the presence and severity of 12 behavioral symptoms. For the MCI and AD groups, factor analyses were conducted on the NPI-Q data. Factors were selected based on the number of eigenvalues > 1, and factor loadings > .40 were considered significant. For the MCI group, ‘mood’ (depression and anxiety) and ‘frontal’ (agitation, disinhibition, and irritability) factors emerged. The analysis for the AD group yielded ‘frontal-behavioral’ (elation and disinhibition), ‘frontal-emotional’ (agitation, apathy, irritability), and ‘psychosis’ (delusions and hallucinations) factors. Our findings indicate that although the two groups share some similar frontal symptoms, mood problems are more common in MCI, while psychotic symptoms are more common in AD. Furthermore, a wider range of frontal symptoms is found in AD. Overall, the behavioral patterns in these groups are qualitatively dissimilar.