Volumetric analysis of hippocampal sub-regions in late onset depression: A 3 tesla magnetic resonance imaging study

• We evaluated sub regional hippocampal volume in late onset depression (LOD).
• Left posterior hippocampal volume is smaller in LOD than healthy control group.
• Right and left posterior hippocampus volume negatively correlated with depression severity.

BackgroundWhile many studies have reported reduced volume of hippocampus in late onset depression (LOD), the status of hippocampus sub-regions (anterior/posterior) is yet to be explored. Evaluating hippocampal sub-regions might facilitate better elucidation of the neurobiological basis of LOD.MethodsTwenty five elderly subjects with LOD (mean age = 65.28 yr, SD = 5.73, 15 females) and 20 healthy controls (mean age = 65.35 yr, SD = 5.67, 7 females) were examined using 3-tesla magnetic resonance imaging (MRI). They were also evaluated with Montgomery Asberg Depression Rating Scale (MADRS) and Hindi Mental State Examination (HMSE). We examined the difference in volume of Hippocampal sub-regions between the LOD group and control group controlling for the age, sex and intracranial volume.ResultsLeft posterior hippocampus volume was significantly smaller in LOD group than the control group (1.01 ± 0.19 ml vs 1.16 ± 0.25 ml, F = 7.50, p = 0.009). There was a similar trend for the right posterior hippocampus (1.08 ± 0.19 ml vs 1.18 ± 0.27 ml, F = 3.18, p = 0.082). Depression severity (mean MADRS score = 20.64 ± 8.99) had a significant negative correlation with volumes of right posterior hippocampus (r = −0.37, p = 0.012) and left posterior hippocampus (r = −0.46, p = 0.001) in the LOD group.ConclusionsSpecific reduction of posterior hippocampus volume and its relationship with depression severity indicates sub region specific hippocampal volumetric abnormalities in LOD. Future studies need to evaluate sub region specific hippocampal volume in LOD longitudinally for better understanding of the pathogenesis of LOD in view of the functional differences between anterior and posterior hippocampus.