Aging
Lateral differences in the relationship between hippocampal volume and depressive symptoms in a cohort of ethnically diverse older adults Suhani Amin* Suhani Amin Amin Amin Leonard Davis School of Gerontology, University of Southern California
Reduced hippocampal volume is associated with depression diagnosis and symptoms in older adults. However, findings on hemispheric differences remain mixed and evidence is limited in ethnically diverse samples. Using the Health and Aging Brain Study (HABS-HD) cohort (n = 2280), we examined the effects of left and right hippocampal volumes on depressive symptoms measured by the 30-item Geriatric Depression Scale (GDS). Outcomes were analyzed both continuously and dichotomously as mild-to-severe (GDS score >= 10) vs. little-to-no symptoms. Model 1 was unadjusted, and Model 2 adjusted for age at imaging, gender, ethnicity (White, Hispanic, Black), education, income, and scanning protocol. Hippocampal volumes were residualized for intracranial volume and z-scored. The sample had a mean age of 69.1 (SD = 6.4), 59.6% female, a racial/ethnic distribution of 42.9% White, 32.8% Hispanic, and 24.3% Black participants, and 17.2% of the sample met criteria for mild-to-severe symptoms. Larger left and right hippocampal volumes were associated with lower GDS scores after adjustment, with a stronger effect for the left hippocampus (β = -0.481 z-score units, 95% CI [-0.725, -0.238], p < 0.001). When modeled dichotomously, only the left hippocampus volume was associated with meaningful reduction in odds of mild-to-severe depressive symptoms (OR = 0.848, 95% CI [0.748, 0.962] p = 0.01). Our analyses find an association between hippocampal volumes and late-life depressive symptoms in an ethnically diverse cohort and identify lateralized effects. Taken together, these findings suggest a notable role of the left hippocampus, which is known to be involved in episodic, contextual, and self-relevant memories, in late-life depressive symptoms.
