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 α (TNFα) 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; β = -0.212, p = .031), verbal memory (F = 5.404, p = .022; β = -0.255, p = .009) and fine motor speed (F = 9.038, p = .003; β = -0.319, p = .001) was observed. Levels of TNFα and fibrinogen were inversely related to inhibitory control (F = 5.055, p = .027; β = -0.226, p = .021) and verbal memory (F = 4.732, p = .032; β = -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.