Objective: This study aimed to clarify the relationship between the epsilon4 allele and late-life depression, taking into account lipid profile, vascular diseases, and sociodemographics.
Methods: Using a multilevel stratified random sampling strategy, a total of 500 subjects aged 65 to 74 years were recruited for this cross-sectional study from the official household records of an entire county in southern Taiwan. Depressive symptoms were assessed by the Taiwanese Depression Questionnaire (TDQ). Cognitive function was assessed by the Short Portable Mental Status Questionnaire. Blood samples were collected for the determination of the apolipoprotein E (ApoE) polymorphism and the lipid profile.
Results: A total of 283 subjects (58.7% male, with a mean age of 69.2 +/- 2.7 years) completed all questionnaires and collection of blood samples. Using the chi(2) test, the overall difference for frequency of the presence of the epsilon4 allele was significant among the severe group (TDQ score >18), moderate group (TDQ score 9-18), and mild group (TDQ score <9). The proportion of history of heart disease was significantly higher in the severe group than in the mild or moderate group. Kruskal-Wallis statistics revealed that the mean total and low-density lipoprotein cholesterol levels were significantly higher in the severe group than in the moderate or mild group. With our two-level four-class latent class regression model, the presence of the epsilon4 allele was significantly associated with the severely depressed group as compared to the nondepressed group, adjusting for vascular diseases and lipid profile.
Conclusion: The ApoE epsilon4 allele may be correlated with severe depression in the elderly through ways other than the "vascular depression" hypothesis.