Background: The epsilon 4 allele of apolipoprotein E (APOE) as well as affective disorder have been found to be associated with Alzheimer's disease, but it is unclear whether cognitive impairment in affective disorder or subtypes of affective disorder is mediated by the epsilon 4 allele of APOE.
Methods: The genotype of APOE was analyzed in 106 unipolar patients, 21 bipolar patients, and 46 controls and correlated with cognitive function in the euthymic phase as measured by the Mini-Mental State Examination, the Cambridge Cognitive Examination, the Mattis Dementia Rating Scale, the Gottfries-Bråne-Steen Dementia Rating Scale, and the Global Deterioration Scale.
Results: The frequency of APOE-epsilon 4 allele was approximately the same in unipolar patients (.189) and in bipolar patients (.167). Although patients showed more cognitive impairment than controls, no significant overall difference was found between the frequency of APOE-epsilon 4 allele in patients (.185) and controls (.131). In fact, the frequency of APOE-epsilon 4 allele did not correlate with cognitive impairment. It was not possible to identify subgroups of patients with an increased frequency of APOE-epsilon 4 allele, as no association was found with gender, age at onset, the number of affective episodes, the presence of psychotic features, or the prevalence of familial affective disorder.
Conclusions: It seems that cognitive impairment in affective disorder can be attributed to pathways other than the APOE genotype.