Midlife obesity has been associated with an increased risk of dementia. The underlying mechanisms are poorly understood. Our aim was to examine the cross-sectional association of body mass index (BMI), waist circumference (WC), waist to hip ratio (WHR) and CT-based measures of subcutaneous (SAT) and visceral (VAT) adipose tissue with various MRI-markers of brain aging in middle-aged community adults.
Participants from the Framingham Offspring cohort were eligible if in addition to having measures of BMI, WC, WHR, SAT and VAT, they had undergone a volumetric brain MRI scan with measures of total brain volume (TCBV), temporal horn volume (THV), white matter hyperintensity volume (WMHV) and MRI-defined brain infarcts (BI). All analyses were adjusted for age, sex and time interval between abdominal CT and brain MRI.
In a sample of 733 community participants (mean age 60 years, 53% women), we observed an inverse association of BMI (estimate by standard deviation unit ± standard error =−0.27±0.12,p=0.02), WC (−0.30±0.12,p=0.01), WHR (−0.37±0.12,p=0.02), SAT (−0.23±0.11,p=0.04) and VAT (−0.36±0.12,p=0.002) with TCBV, independent of vascular risk factors. The association between VAT and TCBV was the strongest and most robust, and was also independent of BMI (−0.35±0.15,p=0.02) and insulin resistance (−0.32±0.13,p=0.01). When adjusting for C-reactive protein levels the associations were attenuated (−0.17±0.13,p=0.17 for VAT). No consistently significant association was observed between the anthropometric or CT-based abdominal fat measures and THV, WMHV or BI.
In middle-aged community participants we observed a significant inverse association of anthropometric and CT-based measures of abdominal, especially visceral, fat with total brain volume.