Cluster Analysis of Behavioral and Psychological Symptoms in Persons with Alzheimer's Disease

Background: Alzheimer’s disease (AD) is the most common neurodegenerative disease. In 2017, an estimated 5.5 million Americans are living with AD. Behavioral and psychological symptoms (BPS) represent a heterogeneous group of non-cognitive symptoms and behaviors occurring in PwAD, and are frequent amongst PwAD, affecting nearly all PwAD at some point in the illness. Recent evidence suggests that AD symptoms “cluster,” however, limited research has been done to identify classifications of PwAD based on their BPS and examine the association between those identified clusters and caregiver burden and depression. This study aims to explore the typologies of PwAD based on their BPS using cluster analysis.

Methods: Data were collected from the South Carolina AD Registry in 2010. The study sample included 705 dyads of PwAD and informal caregivers. Primary measures used in the study were Neuropsychiatric Inventory (12 domains, NPI), Center for Epidemiologic Studies Depression Scale Revised (10 items, CESD-R-10), and the screening version of Zarit Burden Interview (4 items, ZBI). To identify a typology of PwAD, both the presence as well as the severity and frequency of symptoms were considered. Ward’s method of hierarchical cluster analysis was employed using squared Euclidian distances to identify initial clusters. After the classification, the differences between the identified subgroups were tested using an ANOVA for continuous variables: caregiver burden and depression.

Results: Based on the presence of BPS, three subgroups were identified: PwAD with least presence of symptoms (n=200), PwAD with more hypoactive symptoms such as apathy, appetite, and eating changes (n=227), and PwAD with more psychotic symptoms such as delusions, hallucinations, and anxiety (n=214). ANOVA test results showed differences among three clusters on caregiver burden level (F= 56.73, p<.0001) and caregiver depression (F= 34.65, p<.0001). The group with more psychotic symptoms had a higher level of caregiver burden (mean=8.48, SD=3.67) than hypoactive group (mean=7.00, SD=4.04) and minimally symptomatic group (mean=4.51, SD=3.73). Caregivers of PwAD with more psychotic symptoms reported highest level of depression (Mean=12.97, SD=6.48). Pairwise tests showed that average level of caregiver burden and depression for each group were significantly different from each other group.

Based on the severity and frequency of symptoms, a four-cluster solution was determined to be optimal. It demonstrated significant differences in the means of 12 domains of NPI. Cluster 1 (N=304) endorsed the least average score of symptoms; cluster 2 (N=156) included PwAD who had high scores on hyperactive symptoms (e.g., agitation, irritability); in cluster 3 (N=105), high scores on apathetic symptoms (e.g., apathy, aberrant motor behavior, nighttime behavior disorders) were noted; and PwAD in cluster 4 (N=76) were those with severe psychotic symptoms. ANOVA test results showed differences among four clusters on caregiver burden level (F= 41.46, p<.0001) and caregiver depression (F= 38.67, p<.0001).

Conclusions and Implication: The findings inform that PwAD can be categorized based on the presence and severity of symptoms and that such grouping has predictive validity. Practical implications for social workers will be discussed to develop educational programs for caregivers that inform behavioral changes in PwAD and strategies to handle those behaviors.