Structural brain differences and cognitive functioning related to body mass index in older females

Abstract

Little is known about the effect of obesity on brain structures and cognition in healthy older adults. This study examined the association between body mass index (BMI), regional volume differences in gray and white matter measured by magnetic resonance imaging (MRI), and cognitive functioning in older females. Participants included 95 community-dwelling older females (ages 52-92 years) who underwent extensive neuropsychological testing and high-resolution MRI scanning. Optimized voxel-based morphometry techniques were employed to determine the correlation between BMI and regional gray and white matter volumes. Volumes of significant regions were then correlated with cognitive functioning. Higher BMI was associated with decreased gray matter volumes in the left orbitofrontal, right inferior frontal, and right precentral gyri, a right posterior region including the parahippocampal, fusiform, and lingual gyri, and right cerebellar regions, as well as increased volumes of white matter in the frontal, temporal, and parietal lobes, even when hypertension was considered. Compared to normal weight women, obese women performed poorer on tests of executive functioning. Smaller gray matter volume in the left orbitofrontal region was associated with lower executive functioning. Additionally, despite the lack of significant group differences in memory and visuomotor speed, gray and white matter volumes predicted performance on these measures. The results provide additional evidence for a negative link between increased body fat and brain functioning in older females.

Figure 1

Axial sections depict areas of significant negative correlation between body mass index (BMI) and gray matter volume (A), and areas of positive correlation between BMI and white matter volume (B) controlling for age and intracranial vault. Statistical t‐maps from two regression analyses with and without hypertension (HT) included as a covariate were thresholded at P < 0.05 FDR corrected and transferred into binary images. Binary images of both analyses were superimposed on the study‐specific average T1 template image. The maps represent the extent of significantly correlated voxels with and without hypertension as a covariate. Controlling for hypertension tended to decrease the extent of the gray matter volume negatively correlated with BMI, but increased the extent of regions with positive correlations between white matter volume and BMI. The locations of the axonal sections are indicated on the accompanying sagittal section.

Figure 2

Scatter plots showing the relation between body mass index (BMI) and standardized volumes of (A) the left orbital frontal gray matter (MNI coordinates: −33, 49, −7), (B) the right posterior cerebellar gray matter (16, −69, −32), (C) the right orbital frontal white matter (12, 51, −14), and (D) the left temporal stem white matter (−32, −12, −13). Standardized volumes are adjusted for intracranial volume, age, and hypertension.

Figure 3

Scatter plots showing the relation between (A) executive function and the standardized residuals of the proportion of left orbital frontal gray matter volume (MNI coordinates: −33, 49, −7) and (B) memory function and standardized residuals of the proportion of gray matter volume of the right posterior cerebellum (16, −69, −32) after controlling for vocabulary. The regression line is displayed for all subjects (ALL), and for those without hypertension (HT–).