Association of body mass index, and waist to hip ratio with brain structure

Objective: We examined the association of body mass index (BMI) and waist to hip ratio (WHR) with brain volume. Methods: We used cross-sectional data from UK Biobank study (n=9,652 ; aged 55.4±7.5 yrs; 47.9% men). Measures included BMI, WHR, and total fat mass as ascertained from bioimpedance. Brain images were produced using structural magnetic resonance imaging. Results: After adjustment for a range of covariates, higher levels of all obesity measures were related to lower grey matter volume: BMI per SD (beta coefficient=-4113; 95% confidence interval: -4862, -3364), WHR (-4272; -5280, -3264), fat mass (-4590; -5386, -3793). The combination of overall obesity (BMI≥30 kg/m2 ) and central obesity (WHR>0.85 women; >0.90 men) was associated with the lowest grey matter compared with lean adults. In hypothesis-free testing with a Bonferroni correction, obesity was also related to various regional brain volumes including Caudate, Putamen, Pallidum, and Nucelus Accumbens. No associations between obesity and white matter were apparent. Conclusion: The combination of heightened BMI and WHR may be an important risk factor for grey matter atrophy.