Abstract
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Objective:Subjective cognitive complaints are common in individuals with Parkinson’s disease and Essential Tremor. One scale often used to capture the type and severity of subjective cognitive concerns is the Cognitive Change Index-20 (CCI-20). Created by Saykin et al (2006), the CCI-20 is a questionnaire that assesses perception of cognitive changes in memory, executive function, and language domains. Despite its multidomain structure, previous research has not empirically examined whether the CCI-20's underlying factor structure aligns with the cognitive domains proposed during its original development. Thus, the goal of the current study was to investigate the factor structure of the CCI-20 in individuals with movement disorders (Parkinson’s disease, Essential Tremor) who are known to experience varying degrees of cognitive sequelae as part of their disease progression.
Participants and Methods:Participants included a convenience sample of 216 non-demented individuals with Parkinson disease (n=149) or Essential Tremor (n=67) who were seen at the University of Florida Fixel Institute Movement Disorders Center. All received the CCI-20 as part of a neuropsychological evaluation. The CCI-20 consists of 20 items, rated on a 5-point Likert scale, that ask questions about change in memory (12 items), executive function (5 items), and language (3 items) over the past 5 years. An exploratory factor analysis was conducted on CCI-20 scores using Promax rotation with factor extraction based on scree plot visual inspection and Kaiser’s rule (eigenvalues >1.0). Cronbach’s alpha was used to assess internal consistency reliability. Finally, Spearman correlations determined associations between factors and mood measures of depression (Beck Depression Inventory-II, BDI-II), apathy (Apathy Scale, AS), and anxiety (State-Trait Anxiety Inventory, STAI).
Results:Because the Parkinson’s disease and Essential Tremor groups did not statistically differ in their CCI-20 total scores, they were combined into a single group for analyses. This resulted in 216 participants who were well-educated (m=15.01±2.92), in their mid-60's (m=67.72±9.33), predominantly male (63%), and non-Hispanic White (93.6%). The factor analysis resulted in 3 factors: factor 1 included 8 memory items (items 1-4, 6, 10-12; loadings from .524 to .920); factor 2 included all executive and language (items 13-20; loadings from .605 to .824), and factor 3 included four remaining memory items (items 5, 7-9; loadings from .628 to .810). Reliability of the 20 CCI items was good (a = .94), and reliability within each factor ranged from adequate (Factor 3, a = .78) to good (Factors 1 and 2, a = .90). All factors showed significant weak to moderate associations with BDI-II, AS, and STAI (state and trait) scores.
Conclusions:The CCI-20 revealed three distinct dimensions of subjective cognitive complaints that did not correspond to the memory, executive function, and language domains. Rather, the CCI-20 was decomposed into two different dimensions of memory complaints and one dimension of non-memory complaints. Mood symptoms played a significant role in driving all dimensions of subjective cognitive complaints. Future studies should confirm this triadic structure in a healthy older adult sample and explore the relationship between factors and objective cognitive performance beyond the contribution of mood. T32-AG061892; T32-NS082168
