Confirmatory factor analysis of the Cornell scale for depression in dementia among patient with dementia of various degrees

Background: Depression in dementia is difficult to diagnose. The psychometric qualities of the Cornell scale for depression in dementia and whether depression varies depending on the dementia severity are still controversial.

Design: Cross-sectional study of memory clinic and nursing-home patients.

Methods: A sample of 1682 patients (750 from memory clinics and 932 from nursing homes) with Clinical dementia rating scale score of one or higher was evaluated with the Cornell scale. The sample was randomly divided into two groups. Exploratory factor analysis was performed on one-half of the patients and confirmatory factor analysis on the other half. It was further analysed whether the scores of the sub-scales differed across CDR score.

Results: A five-factor solution fitted the data best according to both the exploratory and confirmatory factor analysis: 'mood', 'physical', 'cyclic', 'retardation' and 'behaviour'. Further, it was found that the sum score of the Cornell scale differs significantly across dementia severity (p=0.018). The mood and the cyclic sub-scales scores did not vary across dementia severity, unlike the three remaining sub-scales scores.

Conclusion: A five-factor solution of the Cornell scale best fitted the data according to both exploratory and confirmatory factor analysis. The mood and cyclic factors' scores did not vary across dementia severity, and this might suggest that they are the core symptoms of depression that are equally present regardless of dementia severity. The other factors scores were higher in severe dementia, which might suggest that these factors are related to the dementia.