Thirteen years secular trends reveal a dramatic drop in recommended daily physical activity in Swedish youth a smartphone effect?
Background: Regular physical activity (PA) provides a substantial health benefit for children. Monitoring physical activity would help in developing policies and guidelines to increase activity levels. Evaluation and comparison of physical activity across time have several underlying assumptions. Thus, it is fundamental to compare matching populations, and to use the same measurement technique, instrument and test protocol during similar test conditions. In a study of secular trends of pedometer determined physical activity in 7 9 year old Swedish children, physical activity increased during 2000 2006 and in another study of children aged 13 14 years reported no significant decrease in PA during 2000 2008. Could this positive finding hold true even over a longer time span in Sweden? To our knowledge, longer time spans of pedometer determined PA trends have never been published. Purpose: To explore secular trends of pedometerdetermined physical activity (PA) body mass index (BMI) the percentage to meet recommendations of daily PA and the percentage of overweight/obese from 2000 to 2006 and 2013 in second graders from the very same two schools and from 2000 to 2013 in fifth graders. Methods: Trends between three cross sectional cohorts from five schools in 2000, and from two schools in 2006 and 2013 were analysed. Participating 2nd graders were n 2000 126 (57 girls) in 2006 84 (42 girls) and in 2013 (44 (23 girls) and 5th graders in 2000 105 (53 girls) and in 2013 38 (18 girls) During four consecutive weekdays, physical activity data were collected, height and weight measured, and BMI computed. Identical instruments and procedures were used on all three occasions. One way ANOVA Post hoc Scheffe was applied for analysis. Results: In 2nd grade girls a significant increase of PA from 2000 to 2006 was observed (p< 0.01) and followed by a stable level between 2006 and 2013. No significant differences between the boy's cohorts were seen. In 5th grade boys a significant decrease was observed between 2000 and 2013 with a drop in average daily PA from 16670 to 12704 (p< 0.01) In girls level of PAwas stable between 2000 and 2013. The percentage fulfilling upper endpoint for both boys (15,000 steps) and girls (12000 steps) to achieve the 60minutes of MVPA recommendation was higher in 2013 compared to 2000 for both genders in second grade, for fifth graders it dropped from 71% to 61% and from 76% to 20% between 2000 and 2013 in girls and boys respectively. Conclusion(s) Secular trends of PA differ between boys and girls. 2nd graders and 5th grade girls were largely stable whereas PA in 5th grade boys dropped by 24% between 2000 and 2013. Changing recess and leisure time habits such as smartphone use could be one of the causes. Implications: This study, point out the possible magnitude of unlimited smartphone use during recess or leisure time on children's physical activity and the need to further study this phenomena.