Late-life obesity is associated with smaller global and regional gray matter volumes: a voxel-based morphometric study

Abstract

Objective: Obesity adversely affects frontal lobe brain structure and function. Here we sought to show that people who are obese versus those who are of normal weight over a 5-year period have differential global and regional brain volumes.

Design: Using voxel-based morphometry, contrasts were done between those who were recorded as being either obese or of normal weight over two time points in the 5 years prior to the brain scan. In a post-hoc preliminary analysis, we compared scores for obese and normal weight people who completed the trail-making task.

Subjects: A total of 292 subjects were examined following exclusions (for example, owing to dementia, stroke and cortical infarcts) from the Prospective Investigation of the Vasculature in Uppsala Seniors cohort with a body mass index of normal weight (<25 kg m(-2)) or obese (30 kg m(-2)).

Results: People who were obese had significantly smaller total brain volumes and specifically, significantly reduced total gray matter (GM) volume (GMV) (with no difference in white matter or cerebrospinal fluid). Initial exploratory whole brain uncorrected analysis revealed that people who were obese had significantly smaller GMV in the bilateral supplementary motor area, bilateral dorsolateral prefrontal cortex (DLPFC), left inferior frontal gyrus and left postcentral gyrus. Secondary more stringent corrected analyses revealed a surviving cluster of GMV difference in the left DLPFC. Finally, post-hoc contrasts of scores on the trail-making task, which is linked to DLPFC function, revealed that obese people were significantly slower than those of normal weight.

Conclusion: These findings suggest that in comparison with normal weight, people who are obese have smaller GMV, particularly in the left DLPFC. Our results may provide evidence for a potential working memory mechanism for the cognitive suppression of appetite that may lower the risk of developing obesity in later life.

Figures

Figure 1

The influence of obesity on bilateral DLPFC, bilateral SMA, left IFG and left postcentral gyrus (PCG) (uncorrected). Rendered image of VBM illustrates significant GMV reductions in frontotemporal regions in obese elderly men and women (n=59), as compared with normal-weight subjects (n=97). These analyses were uncorrected and only clusters significant at P<0.05 were reported.

Figure 2

The influence of obesity on the dorsal prefrontal cortex GMV in elderly men and women (corrected). Brain slices of VBM illustrate significant GMV reductions in the left dorsolateral prefronal cortex (DLPFC) in obese elderly men and women (n=59), as compared with normal-weight counterparts (n=97; saggital (left), coronal (right) and axial (bottom) slices). Multiple voxel comparisons were corrected using the family-wise error (FWE) threshold of P<0.05, and a cluster threshold of 50 voxels was applied. Color bar indicates T values.

Figure 3

TMT performance in obese and normal-weight elderly men and women. Time taken to complete the trail-making B test in seconds (corrected for the trail-making A test performance), in a total of 292 stable (at both age 70 and 75 years) obese (BMI⩾30 kg m−2, n=112) and normal-weight (BMI <25 kg m−2, n=180) elderly Swedish men and women. *P<0.04, one tailed after correction for university education.