Neck Circumference and Cerebral Gray Matter Volume.

BACKGROUND While obesity is linked with brain atrophy and dementia incidence, associations with regional adiposity are uncertain. Our goal was to determine whether cerebral gray matter volume is related to neck circumference (NC), a measure of regional adiposity having unique relationships with metabolic disorders and cardiovascular disease. METHODS Magnetic resonance imaging and NC were cross-sectionally assessed from 2011 to 2014 in a population-based sample of 2916 men and women in the Korean Genome and Epidemiology Study. RESULTS For men, NC was inversely associated with total and regional gray matter in the frontal, temporal, and occipital lobes after adjusting for age and intracranial brain volume. Associations were especially strong in the presence of diabetes. With further adjustment for indices of body composition and other characteristics, total and frontal gray matter in diabetic men were lowered by 6.1 mL (95% confidence interval: 2.5-9.7, P=0.004) and 2.9 mL (95% confidence interval: 1.0-4.9, P=0.017), respectively, per SD increase in NC (2.3 cm). For men without diabetes, and in all women, associations were less apparent. CONCLUSIONS In men with diabetes, NC was inversely associated with cerebral gray matter volume. The link between neck anthropometry and brain aging in diabetic men warrants further consideration.