Body Composition Is Not Related to Structural or Vascular Brain Changes

Area of Science:

• Neuroimaging
• Metabolic Health
• Aging Research

Background:

• Obesity, measured by Body Mass Index (BMI), is linked to brain structure and cerebral small vessel disease (CSVD).
• BMI may not fully capture body composition.
• Longitudinal effects of body composition on the brain remain unclear.

Purpose of the Study:

• To investigate cross-sectional and longitudinal associations between detailed body composition measures and brain health.
• To differentiate the impact of fat mass and fat-free mass on brain structure and CSVD markers.

Main Methods:

• Utilized dual-energy X-ray absorptiometry (DXA) for body composition (BMI, fat mass index [FMI], fat-free mass index [FFMI]) and MRI for brain assessments.
• Assessed brain tissue volume, white matter microstructure (fractional anisotropy [FA], mean diffusivity [MD]), and CSVD markers (white matter hyperintensity volume, lacunes, microbleeds).
• Employed multivariable regression models for cross-sectional and longitudinal analyses over a median follow-up of 5.5 years in 1,844 participants.

Main Results:

• Higher BMI and FMI were cross-sectionally linked to smaller white matter volumes and altered white matter microstructure (higher FA and MD).
• Higher FFMI showed a cross-sectional association with larger gray matter volume.
• No statistically significant or clinically relevant longitudinal associations were found between body composition and changes in brain metrics.

Conclusions:

• Body composition, specifically fat mass and fat-free mass, does not appear to directly influence longitudinal changes in brain tissue volume, white matter integrity, or CSVD markers.
• Observed cross-sectional relationships between body composition and brain structure likely reflect shared underlying etiologies or cumulative exposure to risk factors.