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Changes in hippocampal volume in late-life depression may not be due to Alzheimer's disease

Recent findings indicated hippocampal volume was smaller in individuals with late-life depression; however, lower hippocampal volume was not due to higher amyloid deposition.

“With some exceptions, there is accumulating evidence showing that late-life depression is associated with smaller hippocampal volume. However, there is considerable debate about its etiology. The leading hypotheses are the depression-as-late-life-neuropsychiatric-disorder model and the stress model,” François-Laurent De Winter, MD, of University Psychiatric Center, KU Leuven, Belgium, and colleagues wrote.

To assess associations between lower hippocampal volume in late-life depression and Alzheimer’s disease pathology, researchers evaluated 48 currently depressed older adults and 52 age- and gender-matched healthy comparison individuals. Study participants underwent structural MRI, [¹⁸F]flutemetamol amyloid PET imaging, apolipoprotein E genotyping and neuropsychological assessment.

Individuals with depression had significantly lower mean normalized total hippocampal volume, compared with controls (P = .029). However, there was no group difference in distribution or median amyloid load.

Hippocampal volume difference may be due to decreases in the left (P = .017) and right (P = .077) hippocampi, according to researchers.

When excluding amyloid-positive participants, the difference in mean normalized total hippocampal volume remained significant (P = .035).

There were no significant associations between hippocampal volume and amyloid deposition or total hippocampal volume and white matter hypersensitivity volume.

Researchers found a main effect of APOE genotype on amyloid load (P < .001), but not for hippocampal volume.

“In summary, our study challenges the idea that lower hippocampal volume in late-life depression is due to Alzheimer’s disease and encourages the investigation of alternative models,” the researchers concluded. – by Amanda Oldt

Disclosure: De Winter reports no relevant financial disclosures. Please see the full study for a list of all authors’ relevant financial disclosures.