Body mass index predicts lower connectivity in associational fibers of the temporal lobe in older men

Abstract

Increased body mass index (BMI) is related to changes in white matter (WM) connectivity1 . We investigated whether WM connectivity patterns as a function of BMI varies across sex differences.We enrolled 289 individuals (58 CDR=0 & 231 CDR=0.5) from the Knight Alzheimer Disease Research Center (ADRC) (Table 1). Participants were included if they had a physical evaluation within 12 months of a diffusion MRI scan and excluded if they had clinical dementia. Connectome analyses were performed using the DSI Studio software (http://dsi-studio.labsolver.org/). Diffusion data were reconstructed in the MNI space using q-space diffeomorphic reconstruction (QSDR)2 . The quantitative anisotropy was extracted as the local connectome fingerprint. A multi-regression model were used to derive the correlation and a false discovery rate threshold of 0.05 was adopted to select tracts using a deterministic fiber tracking algorithm.A positive association between connectivity in the left arcuate fasciculus (AF) and the left middle cerebellar peduncle in men did not survive regression for age (Figure 1-A). Men also showed a statistically significant negative association between connectivity in the bilateral inferior longitudinal fasciculi (ILF), right inferior fronto-occipital fasciculus (IFOF), the frontoparietal and parahippocampal parts of the right cingulum, the tapetum part of the corpus callosum (CC), right fornix and right corticospinal, corticostriatal, and corticopontine tracts. All of these relationships persisted when co-varying for age (Figure 1-B). Results in women revealed a significant positive correlation between connectivity of the right IFOF, right superior longitudinal fasciculus (SLF), right corticopontine, corticospinal tracts, bilateral reticulospinal tracts, and left arcuate fasciculus (AF) (Figure 2-A) even when controlling for age. Connectivity in the bilateral ILF, right IFOF and the tapetum part of the CC showed an inverse correlation with BMI in women (Figure 2-B).Increased BMI is related to lower structural connectivity in important associational WM fibers of the temporal lobe, particularly in older men.