Depression, Cognition, Apolipoprotein E Genotype: Latent Class Approach to Identifying Subtype

Objectives: Possessing the epsilon 4 allele of apolipoprotein E (APOE-epsilon 4) genotype is associated with cognitive impairment in nondemented older adults. The authors hypothesized that they might find a subtype of depression related to impaired cognitive performance associated with the APOE-epsilon 4 allele. Design: A survey conducted between 2001 and 2003 with APOE genotyping. Setting: Primary care offices in the Baltimore area, Participants: The study sample consisted of 305 adults aged 65 or older with complete information on APOE genotyping and covariates. Measurements: The authors used the latent class model to classify respondents according to symptom criteria of American Psychiatric Association's Diagnostic and Statistical Manual as assessed in the Composite International Diagnostic Interview and the following four measures of cognitive function: the Mini-Mental State Exam, Hopkins Verbal Learning Test, Controlled Oral Word Association Test, and the Brief Test of Attention, The authors examined the relationship between class membership and APOE genotype Results: The latent class model yielded three classes: a nondepressed class, a class with depressive Symptoms and average cognitive functioning, and a class with depressive symptoms (particularly thoughts of death and suicide) and impaired cognitive functioning. Possessing at least one APOE-epsilon 4 allele was not predictive of class membership. Conclusion: A subgroup of elderly patients with depressive symptoms, cognitive impairment, and a high likelihood of experiencing thoughts of death or suicide may exist that may not be related to APOE-epsilon 4. Subgroups of older patients with depressive symptoms may be important to identify because of the association with thoughts of death or suicide and cognitive impairment (Am J Geriatr Psychiatry 2009; 17:344-352)