Using factor mixture analysis to model heterogeneity, cognitive structure and determinants of dementia: an application to the Aging, Demographics and Memory Study

The Aging, Demographics, and Memory Study is the first extensive study of cognitive impairment and dementia of population in the USA. A large sample of participants with ages 71?years or older has answered an in-depth questionnaire which included an extensive cognitive assessment. One of the principal aims of the study was to assign a diagnosis of dementia, cognitive impairment but not demented, or normal to the respondents. Because of this heterogeneity, we apply factor mixture model to the set of neuropsychological measures of the study in order to perform clustering of subjects and dimension reduction simultaneously. Moreover, we consider an extended variant of the model by incorporating a set of demographics and clinical covariates which directly affect the latent variables of the factor mixture model. The interest of the analysis is to investigate whether respondents exhibit the same association of overall cognitive functioning with the covariates or whether groups of respondents exist that exhibit different association with the covariates, indicating different determinants of overall cognitive functioning.