Revising on the run or studying on the sofa: prospective associations between physical activity, sedentary behaviour, and exam results in British adolescents

Background: We investigated prospective associations between physical activity/sedentary behaviour (PA/SED) and General Certificate of Secondary Education (GCSE) results in British adolescents. Methods: Exposures were objective PA/SED and self-reported sedentary behaviours (screen (TV, Internet, Computer Games)/non-screen (homework, reading)) measured in 845 adolescents (14.5y +/- 0.5y; 43.6 % male). GCSE results at 16y were obtained from national records. Associations between exposures and academic performance (total exam points) were assessed using multilevel mixed-effects linear regression adjusted for mood, BMI z-score, deprivation, sex, season and school; potential interactions were investigated. Results: PA was not associated with academic performance. One-hour more accelerometer-assessed SED was associated with (beta(95 % CI)) 6.9(1.5,12.4) more GCSE points. An extra hour of screen time was associated with 9.3(-14.3,-4.3) fewer points whereas an extra hour of non-screen time (reading/homework) was associated with 23.1(14.6,31.6) more points. Screen time was still associated with poorer scores after adjusting for objective PA/SED and reading/homework. Conclusions: An extra hour/day of screen time at 14.5y is approximately equivalent to two fewer GCSE grades (e.g., from B to D) at 16y. Strategies to achieve the right balance between screen and non-screen time may be important for improving academic performance. Concerns that encouraging more physical activity may result in decreased academic performance seem unfounded.