Body mass index, systemic inflammation and cognitive performance in adolescents: A cross-sectional study*

Background: Excessive body weight has been related to lower cognitive performance. One of the mechanisms through which excess body weight may affect cognition is inflammation. Hypothesis: Our hypothesis is that both body mass index (BMI) and circulating levels of inflammatory biomarkers will be negatively related to cognitive performance. Design: Cross-sectional study. Setting: Users of the public health centres of the Consorci Sanitari de Terrassa (Terrassa, Spain) between 2010 and 2017 aged 12-21 years. Participants: One hundred and five adolescents (46 normoweight, 18 overweight, 41 obese). Measurements: Levels of high sensitivity C-reactive protein, interleukin 6, tumour necrosis factor & alpha; (TNF & alpha;) and fibrinogen were determined from blood samples. Cognitive performance was evaluated and six cognitive composites were obtained: working memory, cognitive flexibility, inhibitory control, decision-making, verbal memory, and fine motor speed. A single multivariate general lineal model was used to assess the influence of the four inflammatory biomarkers, as well as participants' BMI, sex, and age on the 6 cognitive indexes. Results: An inverse relationship between BMI and inhibitory control (F = 5.688, p = .019; & beta; = -0.212, p = .031), verbal memory (F = 5.404, p = .022; & beta; = -0.255, p = .009) and fine motor speed (F = 9.038, p = .003; & beta; = -0.319, p = .001) was observed. Levels of TNF & alpha; and fibrinogen were inversely related to inhibitory control (F = 5.055, p = .027; & beta; = -0.226, p = .021) and verbal memory (F = 4.732, p = .032; & beta; = -0.274, p = .005), respectively. Limitations: The cross-sectional nature of the study, the use of cognitive tests designed for clinical purposes, and the use of BMI as a proxy for adiposity are limitations of our study that must be taken into account when interpreting results. Conclusions: Our data indicate that some components of executive functions, together with verbal memory, are sensitive to specific obesity-related inflammatory agents at early ages.

Automated summary

This cross-sectional study found that excessive body weight, as indicated by BMI, and levels of inflammatory biomarkers are negatively associated with cognitive performance. The study suggests that inflammation may be one of the mechanisms through which excess body weight affects cognition.