Table 2 Percentage of schoolchildren with backpack weight higher than 10% of their weight and 95% confidence interval, regarding schoolchildren characteristics

From: Backpack weight and back pain reduction: effect of an intervention in adolescents

  CSE1 % (CI 95%)—CSE2
  Control Intervention p-value Control Intervention p-value
Overall 82.8 (79.3–86.3) 77.2 (74.9–79.5) 0.014 67.1 (62.7–71.5) 65.8 (63.1–68.6) 0.626
Sex
 Boys 81.4 (76.2–86.5) 75.1 (71.7–78.4) 0.057 61.5 (55.0–67.9) 62.3 (58.3–66.2) 0.832
 Girls 84.3 (79.4–89.1) 79.5 (76.3–82.8) 0.131 72.7 (66.8–78.5) 69.4 (65.6–73.2) 0.367
Age
 12-years old 85.0 (80.9–89.2) 78.9 (76.0–81.8) 0.026
 13-years old 78.5 (71.9–85.1) 74.4 (70.4–78.3) 0.304 70.5 (65.1–75.9) 69.3 (65.9–72.8) 0.721
 14-years old 61.4 (53.9–68.8) 60.4 (55.9–64.9) 0.838
Overweight or obesity
 No 91.3 (88.0–94.7) 86.8 (84.3–89.3) 0.047 80.1 (75.4–84.8) 78.7 (75.6–81.7) 0.626
 Yes 67.9 (60.7–75.2) 63.7 (59.6–67.9) 0.335 45.5 (37.9–53.1) 45.8 (41.2–50.4) 0.943
School bag
 Two shoulder straps 83.4 (79.7–87.0) 78.0 (75.6–80.3) 0.020 68.2 (63.6–72.7) 67.5 (64.7–70.2) 0.806
 Other type 75.8 (61.1–90.4) 60.4 (47.2–73.6) 0.142 55.6 (39.3–71.8) 26.1 (13.4–38.8) 0.007
  1. Comparison between control and intervention groups in the first and second grade of compulsory secondary education (CSE1–CSE2)