Behavioral syndromes in mild cognitive impairment and Alzheimer's disease

Background: Behavioral disturbances belong to the core symptoms of dementia and are also common in mild cognitive impairment (MCI). The identification of sets of symptoms is clinically interesting, as interventions targeting syndromes may be more effective than the management of individual symptoms.

Objective: This study aimed to identify, describe, measure, and compare the fundamental behavioral syndromes that underlie the observed behavioral symptoms in MCI and Alzheimer's disease (AD).

Methods: A cross-sectional analysis of baseline data from a prospective, longitudinal study on behavioral symptoms in MCI and dementia was performed. The study population consisted of 270 MCI and 402 AD patients. Behavioral assessment was performed by means of Middelheim Frontality Score (MFS), Behave-AD, Cohen-Mansfield Agitation Inventory (CMAI), and Cornell Scale for Depression in Dementia (CSDD). Principal components factor analysis with Direct Oblimin rotation was carried out on the MFS score ≥5, seven cluster scores of the Behave-AD and the total scores of the CMAI and the CSDD.

Results: We identified three factors explaining behavior in the MCI group: a depression, a psychosis, and an agitation syndrome. Similar factors were found in AD, but the order: an agitation, a depression, and a psychosis syndrome, respectively, and the structure differed slightly. Diurnal rhythm disturbances and frontal lobe symptoms loaded with the depression syndrome in MCI and in AD they loaded with the agitation syndrome. Behavioral syndromes correlated in AD, but not in MCI, and the prevalence and severity of the behavioral syndromes were higher in AD than in MCI, except for the severity of the depression syndrome.

Conclusion: In both MCI and AD, three similar behavioral syndromes exist, but behavior in MCI is more dominated by a depression syndrome, while behavior in AD is more subject to an agitation syndrome.