Doctor of Philosophy
Date of Defense
Robert Paul, PhD
Obesity, commonly measured with body mass index (BMI), is associated with numerous deleterious health conditions and may be a modifier of age-related alterations in brain integrity. Research suggests that white matter integrity observed using diffusion tensor imaging (DTI) is altered with high BMI, but the integrity of specific tracts remains poorly understood. Additionally, no studies have examined fractional anisotropy (FA) of tract integrity in conjunction with neuropsychological evaluation with elevated BMI among older adults. It was hypothesized that elevated BMI would be independently associated with lower white matter integrity and cognitive performance. It was also hypothesized that age and BMI would interact in relation to measures of white matter integrity and cognitive performance. Sixty two healthy older adults aged 51 to 81 were evaluated using DTI and neuropsychological evaluation. Associations were examined between BMI, FA in tracts connecting frontal and temporal lobes, and cognitive ability in domains of executive function, processing speed, and memory. Hierarchical linear regressions were utilized to determine the impact of BMI on FA and cognitive function after accounting for demographics, followed by a test for a BMI by age interaction on FA and cognitive indices. Secondary analyses assessed the sensitivity of DTI diffusivity metrics to elevated BMI, and related tract FA to cognitive performance. After controlling for initial demographic relationships, elevated BMI was associated with lower FA in the uncinate fasciculus, though there was no evidence of an age by BMI interaction relating to FA in this tract. No relationships between BMI and cognition were observed. Secondary analyses did not suggest that DTI diffusivity metrics provide unique information about tract integrity related to high BMI. Overall, results suggest elevated BMI is associated with altered integrity of the uncinate fasciculus. This white matter tract connects frontal and temporal lobes and is involved in memory function. There was no evidence of an age by BMI interaction on FA of the uncinate fasciculus, and BMI did not relate to cognitive performance. Future studies should examine measures of cardiovascular health and systemic inflammation to identify factors influencing relationships between BMI and white matter integrity.
Bolzenius, Jacob, "Structural and cognitive correlates of body mass index in healthy older adults" (2014). Dissertations. 231.