Body mass index and magnetic resonance markers of brain integrity in adults

Obesity and being overweight during adulthood have been consistently linked to increased risk for development of dementia later in life, especially Alzheimer's disease. They have also been associated with cognitive dysfunction and brain structural alterations in otherwise healthy adults. Although proton magnetic resonance spectroscopy may distinguish between neuronal and glial components of the brain and may point to neurobiological mechanisms underlying brain atrophy and cognitive changes, no spectroscopic studies have yet assessed the relationships between adiposity and brain metabolites.

We have utilized magnetic resonance imaging and proton magnetic resonance spectroscopic imaging data from 50 healthy middle-aged participants (mean age, 41.7 +/- 8.5 years; 17 women), who were scanned as control subjects for another study.

After adjustment for age and sex, greater body mass indices (BMIs) correlated with: (1) lower concentrations of N-acetylaspartate (spectroscopic marker of neuronal viability) in frontal (p = 0.001), parietal (p = 0.006), and temporal (p = 0.008) white matter; (2) lower N-acetylaspartate in frontal gray matter (p = 0.01); and (3) lower concentrations of choline-containing metabolites (associated with membrane metabolism) in frontal white matter (p = 0.05).

These results suggest that increased BMI at midlife is associated with neuronal and/or myelin abnormalities, primarily in the frontal lobe. Because white matter in the frontal lobes is more prone to the effects of aging than in other lobes, our results may reflect accelerated aging in individuals with high levels of adiposity. Thus, greater BMI may increase the odds of developing an age-related disease, such as Alzheimer's disease.