Less depressive symptoms are associated with smaller hippocampus in subjective memory impairment

Although individuals with subjective memory impairment (SMI) tend to be at an increased risk for dementia and the majority of them have depressive symptoms, it remains unclear whether SMI with depression is associated with an increased or decreased risk of dementia. The purpose of this study was to investigate the relationship between depressive symptoms and hippocampal/amygdalar volume, a reliable biomarker in the prediction of progression to dementia in SMI. Ninety subjects with SMI participated in the study, and 28 healthy participants without memory complaints served as a normal control (NC) group. 3-D T1-weighted structural MRI scans were completed in all subjects. When the volumes of hippocampus and amygdala were compared among the groups, the SMI group showed significantly smaller volumes than the NC group. When multiple regression analysis was conducted in all subjects, neither hippocampal nor amygdalar volume showed significant interaction effect between group and Geriatric Depression Scale (GDS). However, when the analysis was conducted within each group, lower GDS score was associated with smaller hippocampal volume in the SMI group, and higher GDS score was associated with smaller amygdalar volume in the NC group. Thus, individuals with SMI and less depressive symptoms tend to have smaller hippocampus, which could be associated with more risk of dementia, than normal individuals.