A 9-year prospective population-based study on the association between the APOE*E4 allele and late-life depression in Sweden.

BACKGROUND It is well established that there is an association between the apolipoprotein E (APOE) ε4 allele (APOE*E4) and Alzheimer's disease. It is less clear whether there is also an association with geriatric depression. We examined the relationship between APOE*E4 and 5-year incidence of depression in a Swedish population-based sample of older adults without dementia and excluding older adults who developed dementia within 4 years after the diagnosis of depression. METHODS In 2000-2001, 839 women and men (age range, 70-92 years; mean age, 73.8 years) free from dementia and depression underwent neuropsychiatric and neuropsychological examinations and genotyping of the APOE*E4 allele. Follow-up evaluations were conducted in 2005 and 2009.The association between APOE*E4 allele and 5-year incidence of depression was examined, while avoiding possible confounding effects of clinical or preclinical dementia by excluding participants who had dementia at study entry, subsequently developed dementia during the 9-year follow-up period, or had a decline in Mini-Mental State Examination score of ≥5 points. RESULTS Among subjects without depression at study entry and without dementia or significant cognitive decline during the subsequent 9 years, APOE*E4 was prospectively associated with more severe depressive symptoms (b = 1.56, p = .007), incident minor depression (odds ratio = 1.99 [confidence interval = 1.11-3.55], p = .020), and any depression (odds ratio = 1.75 [confidence interval = 1.01-3.03], p = .048). CONCLUSIONS The presence of the APOE*E4 allele predicted future depression in this Swedish population study, even after excluding depressed individuals who later developed dementia, suggesting that the APOE*E4 allele could potentially identify people at high risk for clinically significant depression.