Leptin status in adolescence is associated with academic performance in high school: a cross-sectional study in a Chilean birth cohort

Abstract

Objective: Leptin is a pleiotropic hormone associated with learning and memory via brain receptors. However, elevated plasma leptin levels may impair cognitive and memory functions. Since individual differences in memory performance affect students' ability to learn, we aimed to study the relation between leptin status in adolescence and school performance.

Design and setting: We studied 568 adolescents aged 16-17 years from Santiago. A cross-sectional analysis was carried out on a birth cohort conducted in Santiago (Chile).

Primary and secondary outcome measures: We measured serum leptin concentration using an enzyme-linked immunosorbent assay. Cut-offs from the Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA) Study for 16-year-olds were used to define abnormally high leptin levels (hyperleptinaemia). Academic performance was measured using high-school grades and grade point average (GPA). Data were collected in 2009-2012; data analysis was performed in 2014.

Results: 15% of participants had hyperleptinaemia. They had significantly lower school grades and GPA compared with participants with normal leptin levels (eg, GPA mean difference=33.8 points). Leptin levels were negative and significantly correlated with school grades in 9th, 10th and 12th. Similarly, it was negatively correlated with high-school GPA. After controlling for health, sociodemographic and education confounders, the chances of having a performance ≥75th centile in students having hyperleptinaemia were 32% (95% CI 0.19% to 0.89%) that of students having normal serum leptin concentration.

Conclusions: In high school students, abnormally high levels of leptin were associated with poorer academic performance. These findings support the idea of a relationship between leptin and cognition. Further research is needed on the cognitive effects of leptin in younger populations.

Keywords: academic performance; adolescents; cognition; hyperleptinemia; leptin.

Figure 1

Mean values of serum leptin in adolescents in the sample, by weight status (n=568). Analysis of covariance (ANCOVA) was used in testing differences in serum leptin concentrations stratified by weight status (normal weight, overweight, obesity). Bonferroni's adjustments for multiple comparisons were used to examine the contrasts between the groups. (a) Significantly different from the normal weight group. (b) Significantly different from the overweight group. Normal weight: Body mass index (BMI) z-score from −1 to 1 SD. Overweight: BMI z-score from >1 to 2 SD. Obesity: BMI z-score from >2 SD. Mean values are shown with error bars representing SE.

Figure 2

High-school grades and final grade point average (GPA) in Chilean youths by leptin status at age 16–17 (n=568). Differences in school performance by leptin status in adolescence. Grades and GPA expressed as standardised scores according to the Chilean Ministry of Education. Hyperleptinaemia defined according to the cut-offs published by Köster-Weber et al. Adjustments were made for sex, weight status (overweight and obesity) and insulin sensitivity (homeostasis model assessment of insulin resistance >2.6) at 16–17 years. Mean values are shown with error bars representing SE. Significance: *p<0.05; **p<0.01; ***p<0.001.