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Leisure time computer use and adolescent bone health - findings from the Tromso Study, Fit Futures: a cross-sectional study

Leisure time computer use and adolescent bone health - findings from the Tromso Study, Fit Futures: a cross-sectional study
Leisure time computer use and adolescent bone health - findings from the Tromso Study, Fit Futures: a cross-sectional study
Objectives: low levels of physical activity may have considerable negative effects on bone health in adolescence, and increasing screen time in place of sporting activity during growth is worrying. This study explored the associations between self-reported screen time at weekends and bone mineral density (BMD).

Design: in 2010/2011, 1038 (93%) of the region’s first-year upper-secondary school students (15–18?years) attended the Tromsø Study, Fit Futures 1 (FF1). A follow-up survey (FF2) took place in 2012/2013. BMD at total hip, femoral neck and total body was measured as g/cm² by dual X-ray absorptiometry (GE Lunar prodigy). Lifestyle variables were self-reported, including questions on hours per day spent in front of television/computer during weekends and hours spent on leisure time physical activities. Complete data sets for 388/312 girls and 359/231 boys at FF1/FF2, respectively, were used in analyses. Sex stratified multiple regression analyses were performed.

Results: many adolescents balanced 2–4?h screen time with moderate or high physical activity levels. Screen time was positively related to body mass index (BMI) in boys (p=0.002), who spent more time in front of the computer than girls did (p<0.001). In boys, screen time was adversely associated with BMDFF1 at all sites, and these associations remained robust to adjustments for age, puberty, height, BMI, physical activity, vitamin D levels, smoking, alcohol, calcium and carbonated drink consumption (p<0.05). Screen time was also negatively associated with total hip BMDFF2 (p=0.031). In contrast, girls who spent 4–6?h in front of the computer had higher BMD than the reference (<2?h).

Conclusions: in Norwegian boys, time spent on screen-based sedentary activity was negatively associated with BMD levels; this relationship persisted 2?years later. Such negative associations were not present among girls. Whether this surprising result is explained by biological differences remains unclear
e006665
Winther, A.
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Ahmed, L.A.
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Furberg, A.S.
19ee1356-90b8-4dd1-aeac-f601effd4849
Grimnes, G.
ba1fa94f-f73d-434f-9fc9-bc84f6519649
Jorde, R.
8fa55678-cc6b-43dc-ae68-5376b84c23b7
Nilsen, O.A.
97d7bfdd-166c-4f63-83b3-5a74c84d4110
Dennison, E.
ee647287-edb4-4392-8361-e59fd505b1d1
Emaus, N.
30d14a5c-4b84-4151-a705-36f700ef6e96
Winther, A.
04a0f191-c458-4b1c-b48e-8b5e17848235
Ahmed, L.A.
834ccfd6-5a20-459d-9bbf-8a70ebfcfe74
Furberg, A.S.
19ee1356-90b8-4dd1-aeac-f601effd4849
Grimnes, G.
ba1fa94f-f73d-434f-9fc9-bc84f6519649
Jorde, R.
8fa55678-cc6b-43dc-ae68-5376b84c23b7
Nilsen, O.A.
97d7bfdd-166c-4f63-83b3-5a74c84d4110
Dennison, E.
ee647287-edb4-4392-8361-e59fd505b1d1
Emaus, N.
30d14a5c-4b84-4151-a705-36f700ef6e96

Winther, A., Ahmed, L.A., Furberg, A.S., Grimnes, G., Jorde, R., Nilsen, O.A., Dennison, E. and Emaus, N. (2015) Leisure time computer use and adolescent bone health - findings from the Tromso Study, Fit Futures: a cross-sectional study. BMJ Open, 5 (6), e006665. (doi:10.1136/bmjopen-2014-006665). (PMID:26063563)

Record type: Article

Abstract

Objectives: low levels of physical activity may have considerable negative effects on bone health in adolescence, and increasing screen time in place of sporting activity during growth is worrying. This study explored the associations between self-reported screen time at weekends and bone mineral density (BMD).

Design: in 2010/2011, 1038 (93%) of the region’s first-year upper-secondary school students (15–18?years) attended the Tromsø Study, Fit Futures 1 (FF1). A follow-up survey (FF2) took place in 2012/2013. BMD at total hip, femoral neck and total body was measured as g/cm² by dual X-ray absorptiometry (GE Lunar prodigy). Lifestyle variables were self-reported, including questions on hours per day spent in front of television/computer during weekends and hours spent on leisure time physical activities. Complete data sets for 388/312 girls and 359/231 boys at FF1/FF2, respectively, were used in analyses. Sex stratified multiple regression analyses were performed.

Results: many adolescents balanced 2–4?h screen time with moderate or high physical activity levels. Screen time was positively related to body mass index (BMI) in boys (p=0.002), who spent more time in front of the computer than girls did (p<0.001). In boys, screen time was adversely associated with BMDFF1 at all sites, and these associations remained robust to adjustments for age, puberty, height, BMI, physical activity, vitamin D levels, smoking, alcohol, calcium and carbonated drink consumption (p<0.05). Screen time was also negatively associated with total hip BMDFF2 (p=0.031). In contrast, girls who spent 4–6?h in front of the computer had higher BMD than the reference (<2?h).

Conclusions: in Norwegian boys, time spent on screen-based sedentary activity was negatively associated with BMD levels; this relationship persisted 2?years later. Such negative associations were not present among girls. Whether this surprising result is explained by biological differences remains unclear

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Accepted/In Press date: 20 March 2015
Published date: 22 April 2015
Organisations: MRC Life-Course Epidemiology Unit

Identifiers

Local EPrints ID: 381160
URI: http://eprints.soton.ac.uk/id/eprint/381160
PURE UUID: 5f56789b-c56d-437b-aa72-20a5eeb154f4
ORCID for E. Dennison: ORCID iD orcid.org/0000-0002-3048-4961

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Date deposited: 25 Sep 2015 09:34
Last modified: 15 Mar 2024 02:51

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Contributors

Author: A. Winther
Author: L.A. Ahmed
Author: A.S. Furberg
Author: G. Grimnes
Author: R. Jorde
Author: O.A. Nilsen
Author: E. Dennison ORCID iD
Author: N. Emaus

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