Posterior Cingulate and Lateral Parietal Gray Matter Volume in Older Adults with Depressive Symptoms

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Abstract
Depressive symptoms occurring late in life are an important risk factor for Alzheimer’s disease (AD). The latest research finds that onset of depressive symptoms in late life may herald the development of AD, not only for amnestic Mild Cognitive Impairment (aMCI) patients, but also for cognitively-normal older adults. Neuroimaging of brain structure, blood flow, and glucose metabolism indicates that depressive symptoms in late life are accompanied by structural and functional changes in limbic brain regions vulnerable to AD. The present cross-sectional study was guided by the hypothesis that compared to their non-depressed counterparts, older adults with mild to moderate depressive symptoms have less volume in limbic structures vulnerable to changes in AD—specifically, cortical midline structures such as anterior cingulate and posterior cingulate cortex as well as mesial temporal regions such as bilateral hippocampi and amygdalae. Consistent with our hypothesis, results of a voxel-based morphometry analysis revealed smaller retrosplenial, posterior cingulate, and precuneus gray matter volumes in depressed individuals relative to healthy controls. Right lateral parietal cortex—another region vulnerable to change in AD—was also smaller in the group with depressive symptoms. Contrary to our hypothesis, no volumetric differences were found in the anterior cingulate cortex or mesial temporal lobe. Results of this study show a relationship between geriatric depressive symptoms and brain volume in regions vulnerable to AD. Follow-up of participants over time will tell if brain changes detected here predict development of AD.