Relationship of changes in cognitive and depressive symptoms during antidepressant treatment of individuals with geriatric depression and their relationship to the APOE epsilon 4 allele

BACKGROUND: Co-occurring cognitive impairment in geriatric depression may not improve with antidepressant treatment and it may progress to dementia. AIM: Assess the relationship between changes in cognitive and depressive symptoms among patients with geriatric depression and their association with the APOE epsilon 4 allele before and after antidepressant treatment. METHODS: The presence of the APOE epsilon 4 allele was assessed in 64 incident cases of geriatric depression and 31 elderly individuals without depression and the Geriatric Depression Scale (GDS), Mini-Mental State Examination (MMSE), digit span test, and Trail Making Tests A and B (TMT-A, TMT-B) were administered to these subjects at baseline and 12 months after baseline, during which time the depressed group received standardized treatment with selective serotonin reuptake inhibitors (SSRIs). RESULTS: Prior to treatment patients with geriatric depression had significantly worse cognitive functioning than control subjects and 31 (48%) met criteria for mild cognitive impairment (MCI). After treatment depressed patients with and without comorbid MCI both had significant improvements in their depressive and cognitive symptoms, but those with MCI had more residual symptoms. The severity of cognitive symptoms was not associated with the severity of depressive symptoms at baseline, but they were positively correlated at the 12-month follow-up. The APOE epsilon 4 allele was identified in 14% (9/64) of the patients and in 3% (1/31) of the controls (Fisher's Exact Test, p=0.158). Compared to depressed patients without the allele, depressed patients with the allele had more severe cognitive deficits both before and after treatment, though only some of these differences were statistically significant. CONCLUSIONS: There is substantial cognitive impairment in elderly individuals with geriatric depression. Both the depressive and cognitive symptoms improve with standard SSRI treatment, but individuals with comorbid MCI have more residual depressive and cognitive symptoms after treatment. The APOE epsilon 4 allele is associated with greater cognitive impairment in geriatric depressed patients and may be associated with less responsiveness of cognitive symptoms to antidepressant treatment.