Table 4

Average annual change in sedentary time and in light and moderate and vigorous physical activity over three time points: baseline (age 9/10 years), +1 year (age 10/11 years) and +4 years (age 13/14 years)

 Sedentary (min)Light intensity PA (min)MVPA (min)
β Coefficient95% CIp Valueβ Coefficient95% CIp Valueβ Coefficient95% CIp Value
All days combined
Age (years)10.69.1 to 12.2<0.001−8.9−10.1 to −7.8<0.001−3.9−4.8 to −3.0p<0.001
Sex (reference category: boys)
Girls13.18.8 to 17.4<0.00111.0−4.7 to 26.70.16837.5949.9 to −25.3 p<0.001
Sex–age interaction (reference category: boys)
Girls−1.6−4.4 to 1.10.2481.73.1 to0.20.0221.890.8 to 3.0 p=0.001
Age (years)7.25.4 to 8.9<0.0018.69.8 to7.4<0.0012.803.7 to1.9<0.001
Sex (reference category: boys)
Girls17.212.9 to 21.5<0.0017.71−8.2 to 23.70.34334.046.3 to21.7<0.001
Sex–age interaction (reference category: boys)
Girls−2.1−5.0 to 0.80.1521.53.0 to0.10.0371.50.4 to 2.60.009
Weekend days
Age (years)13.410.2 to 16.5<0.00110.411.8 to9.0<0.0016.658.1 to5.2<0.001
Sex (reference category: boys)
Girls50.64.4 to 96.80.032−3.5−7.0 to 0.10.05246.667.3 to25.9<0.001
Sex–age interaction (reference category: boys)
Girls4.28.4 to0.10.047#2.81.0 to 4.70.003
  • Results are from three level mixed effects linear regression with levels: age, individual and baseline school. Participants with ≥2 time points are included in the models. Results are from models using activity outcomes derived for all days combined (n=990), and separately for weekdays (n=980) and weekend days (n=815). Age–sex interactions were tested for all models. β Coefficients represent the per year changes in the physical activity outcomes.

  • Interpretation: For the all days MVPA model, the average decrease per year of age is 3.9 min/day in boys and 2 min/day (ie, −3.9+1.9) in girls. At age 0, girls do on average 37.6 less min/day than boys, but at age 10 (approximately baseline) this would be (−37.6+10×(1.9)) 18.7 less and at age 14 this would be (−37.6+14×(1.9)) 11.1 less. #This model did not converge.

  • MVPA, moderate and vigorous physical activity; PA, physical activity.