Lean Body Mass, but Not Fat Mass, Is Associated with Hippocampal Memory Performance (P14-011-19)

A converging body of evidence indicates elevated weight status is inversely related to memory forms that disproportionately rely on the hippocampus. However, much of this work has relied on BMI, resulting in a limited understanding of the impact of body composition on memory performance. Accordingly, this study investigated the influence of soft tissue compartments (i.e., lean and fat mass) on hippocampal-dependent memory function. Using a mnemonic discrimination task, we examined lure discrimination, a measure of hippocampal memory ability. It was anticipated that lean body mass would relate positively, and fat mass negatively to lure discrimination ability. Participants included 216 individuals (134 females) between the ages of 25 and 46 years. Participants provided demographic information such as sex, age, and income. Dual energy x-ray absorptiometry (DXA) was used to assess height-adjusted lean and fat mass (LMI and FMI, respectively). Lure discrimination, the ability to correctly identify objects similar to those seen during encoding, was assessed using the Mnemonic Similarity Task (MST). Bivariate correlations were conducted to determine demographic predictors of task performance. Subsequently, a linear regression model controlling for significant predictors was used to determine LMI and FMI influence on lure discrimination. Preliminary data analysis showed a positive correlation between BMI and MST performance. Follow-up bivariate correlations revealed an underlying positive association between LMI and lure discrimination (r = .153, P = .029), while FMI and lure discrimination were not significantly associated (r = .087, P = .218). A linear regression model controlling for age and income showed LMI accounted for a significant proportion of variance in lure discrimination (R² = .070, P = .002), adjusting for demographic variables. These findings indicate that while BMI is related to lure discrimination, this effect appears to be driven by LMI, but not FMI. Future studies are warranted to determine the impact of changes in lean mass on hippocampal memory performance. Funding provided by the Department of Kinesiology and Community Health at the University of Illinois and the USDA National Institute of Food and Agriculture, Hatch Project 1009249. Partial support provided by the Hass Avocado Board.