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A recent analysis of the Bogalusa Heart Study suggests that a higher body mass index (BMI) from early adulthood to midlife is associated with better cognitive function in midlife, particularly among men and Black adults in the United States.
Unexpected Findings on BMI and Cognition
Lead author Kathryn Gwizdala, PhD, a clinical research consultant based in Chicago, expressed surprise at the findings. “We expected to find what you would call the intuitive relationship—that is, greater BMI would be correlated to worse cognitive function in midlife,” Gwizdala told Medscape Medical News. “However, we found what we could consider to be a counterintuitive relationship—that is, greater BMI was correlated with better memory among certain sex and race groups.”
Although BMI has been criticized as a direct measure of adiposity, Gwizdala noted that it remains a widely used metric for population-based studies due to its simplicity and correlation with body fat levels.
Study Details and Key Findings
The Bogalusa Heart Study has tracked participants from childhood to adulthood since 1973. Adiposity was measured using BMI at biannual visits from 1973 to 2016, and cognitive function was assessed in 1,292 participants between 2013 and 2016, when they were between 40 and 58 years old. The study sample consisted of 59% women and 34% Black American individuals.
BMI was recorded at various life stages, with childhood/adolescence BMI being within the healthy range, while early adulthood and midlife BMI fell within the overweight and class 1 obesity ranges. Cognitive tests included measures of memory recall, digit span tasks, and trail-making tests.
The results indicated that greater BMI in early adulthood and midlife was associated with better global cognition and memory performance among men. Additionally, among Black American individuals, higher BMI in early adulthood and midlife correlated with better logical memory performance.
Potential Explanations and Considerations
The researchers acknowledged that previous studies on adiposity and cognition have yielded mixed results. One possible explanation for the positive association found in this study is that earlier research may have suffered from attrition bias, excluding individuals with both high BMI and low cognitive function. Another possibility is that the cognitive effects of adiposity depend on the stage of life when BMI is measured.
Behavioral and biological factors could also play a role in the observed differences by sex and race. The authors suggested that disparities in brain health between Black and White American individuals might influence how adiposity impacts cognitive function.
Expert Commentary: The Complexity of BMI and Cognition
Priya Jaisinghani, MD, a clinical assistant professor at NYU Grossman School of Medicine, commented on the study, noting that it adds to the complex and inconsistent literature on adiposity and cognition. “While BMI is a convenient and widely used population-level tool, it has well-recognized limitations. It does not differentiate between lean and fat mass, fails to account for body fat distribution, and overlooks gender and ethnic differences,” she said.
Jaisinghani also highlighted the influence of confounding factors such as genetics, behavior, socioeconomic status, and broader social determinants of health. She suggested further research incorporating biomarkers, neuroimaging, and lifestyle factors to clarify the relationship between adiposity and cognitive outcomes.
Study Funding and Disclosures
This study was funded by the U.S. National Institute on Aging and the Pennington Biomedical Research Foundation. The authors disclosed no competing interests. Jaisinghani reported affiliations as a speaker for Eli Lilly and Novo Nordisk.
Disclaimer: This article summarizes research findings and does not constitute medical advice. BMI is a widely debated metric, and its implications for health vary by individual. Readers should consult healthcare professionals for personalized guidance on maintaining cognitive and physical well-being.
