Physical activity decreased by a quarter in the 11- to 12-year-old Swedish boys between 2000 and 2013 but was stable in girls: A smartphone effect?

Aim This study explored physical activity, body mass index (BMI) and overweight and obesity from 2000 to 2013 using a convenience sample of second- and fifth-grade Swedish schoolchildren aged 8–9 years and 11–12 years, respectively. Methods We examined cross-sectional cohorts of 126 second-grade children in 2000, 84 in 2006 and 44 in 2013 and 105 fifth-grade children in 2000 and 38 in 2013. No fifth graders were available in 2006. Physical activity data were collected based on pedometer readings over four consecutive weekdays, and height and weight were measured. Identical instruments and procedures were used in all three years. Results There was an increase in physical activity in second-grade girls from 2000 to 2006 (p < 0.01), which then stabilised between 2006 and 2013, but second-grade boys and fifth-grade girls were stable throughout the study period. Fifth-grade boys decreased significantly (24%) from 16 670 to 12 704 steps per day (p < 0.01) from 2000 to 2013. Mean BMI scores remained stable over time. Conclusion Time trends in physical activity differed between boys and girls. Second-grade boys and fifth-grade girls were stable throughout, whereas second-grade girls increased from 2000 to 2006 before stabilising. Fifth-grade boys showed a significant 24% reduction from 2000 to 2013. Changes in recess and leisure time habits, such as smartphone use, may have influenced the result.

"Boys were significantly more active than girls in all the cohorts and grades, except for the fifth grade of the 2013 cohort, where no significant difference was observed: second-grade 2000 (p ≤ 0.00), 2006 (p = 0.025), 2013 (p = 0.13) and fifth-grade 2000 (p ≤ 0.00).... When we studied mean steps per day, we found that physical activity increased in second-grade girls between 2000 and 2006 and was then stable until 2013. It was also stable between 2000 and 2013 in second-grade boys and fifth-grade girls. However, there was a dramatic decrease of 24% among fifth-grade boys during this 13-year period, and this observation is in line with the general consensus and reports 1, 2, suggesting a decline of physical activity among children.... As a result of the structured and detailed observations carried out during recess breaks in the school day as a part of the KIDSCAPE II study, the authors were aware of the frequent use of smartphones in grade five especially in boys, which led to greater physically inactivity during breaks. A teacher in one of the two schools revealed that 100% of the children had access to smartphones during the measurement week. The frequency of smartphone use in Sweden grew rapidly from 2010 to 2013, from 0% to 13% in second-grade pupils and 3% to 53% in fifth-grade pupils. More than a fifth (22%) of fifth-grade boys and 8% of fifth-grade girls have been reported to spend more than three hours a day on the Internet. Corresponding figures for playing computer games are 22% in boys and 4% in girls. Both playing computer games, normally of longer duration, and the use of Internet are possible to do on smartphones and tablets. This might partly explain the difference we found between the physical activity levels of fifth-grade boys and girls in this study...." (Authors, 810, 811)