Hippocampal volume is related to body mass index in Alzheimer's disease

Abstract

Obesity is associated with lower brain volumes in early Alzheimer's disease, but its effects on hippocampal volumes are unclear, as weight loss is also associated with Alzheimer's disease. To address this question, we applied an automated hippocampal mapping method to brain MRI scans for 162 patients with Alzheimer's disease. We hypothesized that obesity, measured by body mass index, would be associated with lower hippocampal volumes in mildly affected patients. Statistical maps showed a selective pattern of hippocampal volume differences that were significantly associated with body mass index. Associations were detected in the anterior hippocampus, and confirmed by permutation testing. Cardiovascular risk factors, such as high body mass index, may promote additional neurodegenerative changes, and should therefore be considered in epidemiological studies and clinical trials.

Fig. 1

Average hippocampal volumes [(millimeter)³] are shown for 162 patients with Alzheimer’s disease. Error bars denote standard errors of the mean. Left, right, and total hippocampal volumes are graphed for normal, overweight, and obese groups.

Fig. 2

Three-dimensional maps show local differences in hippocampal structure associated with BMI in 162 patients with Alzheimer’s disease. (a) Shows the top view of the hippocampi, and (b) shows the view from below. The left hippocampus is on the left side of each pair.