APOE genotype predicts depression in women with Alzheimer's disease: A retrospective study

The association between the epsilon-4 type allele of apolipoprotein E (APOE e4) and depression was investigated in 323 AD patients. Patients were divided into two groups based on the presence (n=61) or absence (n=262) of depression as assessed by the DSM-based Diagnostic Interview Schedule. Both subgroups were demographically comparable with regard to age, education, gender, and severity of cognitive impairment. Analysis of the frequency of APOE e4 alleles between the groups revealed a significantly higher prevalence rate of the APOE e4 genotype in the depressed group (72% of depressed AD patients carried at least one copy of the e4 allele) compared to the non-depressed AD patients (58%). This effect was primarily accounted for by women. Specifically, an interaction was revealed wherein women who possessed the APOE e4 allele were almost 4 times more likely to be depressed in comparison to those who did not carry the allele, and APOE e4 status did not predict depression among men in our sample. These results are consistent with recent suggestions that the APOE e4 genotype may be over-represented among women with AD and depression and highlight a need for additional research investigating the links between APOE genotype, mood, and gender.