MedicalResearch.com Interview with:
Anne Winther Msc
Department of Health and Care Sciences, UiT The Arctic University of Norway
Division of Rehabilitation Services, University Hospital of North Norway, Tromsø, Norway
Medical Research: What is the background for this study? What are the main findings?
Response: Norway has one of the highest reported incidences of osteoporotic fractures in the world. Research on fracture risk has primarily focused on bone mass in the elderly. However, there is a growing awareness of the importance of bone mass during growth as a compensation for the inevitable bone loss and prevention of fractures in the elderly . A recent study on Norwegian adolescents´ lifestyle and bone health concluded that peak bone mass seem to be modifiable by lifestyle factors as higher physical activity levels were strongly associated with bone mass. The other way around; low levels of physical activity may have considerable negative effects on bone health, and increasing sedentary behavior in place of sports and play during growth is worrying. In this study we explored the associations between self-reported hours spent in front of television/computers during weekends along with self reported hours spent on leisure time physical activities and bone mass density (BMD) levels at the hip. This population based study, Fit Futures 1 consisting of 388 girls and 359 boys 15-17 years old was conducted in 2010/2011, and repeated two years later including 66% of the original cohort (Fit Futures 2; 312 girls and 231 boys).
Boys spent more time in front of computers and television than girls; approximately 5 and 4 hours, compared with 4 and 3 hours daily in weekends and weekdays, respectively.
Physical activity levels were adversely related to leisure time computer use at weekends. However, 20 % of the girls and 25 % of the boys balanced 2-4 hours in front of the screen daily with more than 4 hours of sports and hard training per week.
Screen time at weekends was negatively associated with bone mass density levels in boys and positively in girls, after adjustments of several confounders known to affect bone, including age, puberty, physical activity levels and weekday screen time.
Moreover; these contrasting patterns persisted two years later.
Medical Research: What should clinicians and patients take away from your report?
Response: Screen based sedentary behavior has a negative influence on bone in adolescent boys, whereas participation in recreational sports or performing sports at a competitive level seems to exert significant beneficial effect on bone health. The best way to promote good bone health in this age group as well as further into adulthood is to encourage participation in sports and play, as physical activity during adolescence promote physical activity practice in later life.
Medical Research: What recommendations do you have for future research as a result of this study?
Response: These results should be followed up more than 2 years in longitudinal studies , including changes in both exposure and outcome variables. lt would also be preferable with objective measurements of sedentary behavior and physical activity.
The gender difference is striking, and the explanation unclear. Study of body composition in terms of fat mass and lean mass, and their relationships to bone mass may shed light of these differences
Anne Winther Msc, Department of Health and Care Sciences, UiT The Arctic University of Norway, & Division of Rehabilitation Services, University Hospital of North Norway, Tromsø, Norway (2015). More Screen Time Linked To Lower Bone Mass In Boys MedicalResearch.com