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 (β(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.
MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Box 285 Institute of Metabolic Science, Cambridge Biomedical Campus, Cambridge, CB2 0QQ, UK. klc29@medschl.cam.ac.uk.|UKCRC Centre for Diet and Activity Research (CEDAR), MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Box 285 Institute of Metabolic Science, Cambridge Biomedical Campus, Cambridge, CB2 0QQ, UK. klc29@medschl.cam.ac.uk.
Kirsten
K
Corder
UKCRC Centre for Diet and Activity Research (CEDAR), MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Box 285 Institute of Metabolic Science, Cambridge Biomedical Campus, Cambridge, CB2 0QQ, UK. aa595@medschl.cam.ac.uk.
Andrew J
AJ
Atkin
Developmental Psychiatry Section, Department of Psychiatry, University of Cambridge, Douglas House, 18b Trumpington Road, Cambridge, CB2 8AH, UK. drdianebamber@gmail.com.|Cambridge and Peterborough NHS Foundation Trust, Cambridge, UK. drdianebamber@gmail.com.
Diane J
DJ
Bamber
MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Box 285 Institute of Metabolic Science, Cambridge Biomedical Campus, Cambridge, CB2 0QQ, UK. soren.brage@mrc-epid.cam.ac.uk.
Soren
S
Brage
Developmental Psychiatry Section, Department of Psychiatry, University of Cambridge, Douglas House, 18b Trumpington Road, Cambridge, CB2 8AH, UK. vjd20@medschl.cam.ac.uk.|Cambridge and Peterborough NHS Foundation Trust, Cambridge, UK. vjd20@medschl.cam.ac.uk.
Valerie J
VJ
Dunn
MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Box 285 Institute of Metabolic Science, Cambridge Biomedical Campus, Cambridge, CB2 0QQ, UK. ulf.ekelund@nih.no.|Department of Sports Medicine, Norwegian School of Sports Sciences, Oslo, Norway. ulf.ekelund@nih.no.
Ulf
U
Ekelund
Developmental Psychiatry Section, Department of Psychiatry, University of Cambridge, Douglas House, 18b Trumpington Road, Cambridge, CB2 8AH, UK. matthewowensuk@gmail.com.|Cambridge and Peterborough NHS Foundation Trust, Cambridge, UK. matthewowensuk@gmail.com.|Mood Disorders Centre, University of Exeter, Perry Road, Exeter, EX4 4QG, UK. matthewowensuk@gmail.com.
Matthew
M
Owens
MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Box 285 Institute of Metabolic Science, Cambridge Biomedical Campus, Cambridge, CB2 0QQ, UK. ev234@medschl.cam.ac.uk.|UKCRC Centre for Diet and Activity Research (CEDAR), MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Box 285 Institute of Metabolic Science, Cambridge Biomedical Campus, Cambridge, CB2 0QQ, UK. ev234@medschl.cam.ac.uk.
Esther M F
EM
van Sluijs
Developmental Psychiatry Section, Department of Psychiatry, University of Cambridge, Douglas House, 18b Trumpington Road, Cambridge, CB2 8AH, UK. ig104@cam.ac.uk.|Cambridge and Peterborough NHS Foundation Trust, Cambridge, UK. ig104@cam.ac.uk.
Ian M
IM
Goodyer
D000124:Achievement; D000293:Adolescent; D003201:Computers; D003430:Cross-Sectional Studies; D004521:Educational Measurement; D015444:Exercise; D005260:Female; D006801:Humans; D020407:Internet; D008297:Male; D009043:Motor Activity; D011446:Prospective Studies; D012574:Schools; D057185:Sedentary Behavior; D057566:Self Report; D013690:Television; D006113:United Kingdom