Tabla 4 Back pain prevalence in boys and girls in the third grade of compulsory secondary education (CSE3), regarding their characteristics

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

  % (95 CI%)—boys % (95 CI%)—girls
  Control Intervention p-value Control Intervention p-value
Overall 23.5 (19.6–27.7) 23.5 (18.4–29.3) 0.990 38.7 (34.2–43.3) 29.9 (24.7–35.6) 0.015
Age
 14-years old 21.7 (16.2–28.1) 22.4 (15.6–30.4) 0.885 32.2 (26.4–38.5) 25.3 (18.9–32.6) 0.130
 15-years old 22.0 (15.9–29.1) 23.8 (15.2–34.4) 0.740 44.0 (36.3–51.9) 30.3 (21.0–41.0) 0.033
 16-years old 31.2 (21.1–42.7) 27.3 (13.3–45.5) 0.683 50.9 (37.3–64.4) 55.2 (35.7–73.6) 0.706
BMI categories
 Low weight/average weight 21.4 (16.7–26.8) 20.8 (14.5–28.4) 0.893 38.4 (33.1–43.8) 29.3 (23.1–36.2) 0.034
 Overweight/obesity 26.8 (20.3–34.2) 27.1 (19.0–36.6) 0.954 39.4 (31.2–48.1) 31.4 (21.8–42.3) 0.225
School bag
 Two shoulder straps 23.6 (19.7–28.0) 23.5 (18.3–29.3) 0.963 38.4 (33.6–43.4) 30.0 (24.5–35.9) 0.026
 Other types 18.8 (4.1–45.7) 25.0 (0.6–80.6) 0.780 40.3 (28.9–52.5) 29.4 (10.3–56.0) 0.407
Backpack weight > 10% of body weight
 No 24.7 (19.5–30.5) 24.5 (17.6–32.5) 0.958 33.7 (26.5–41.6) 29.8 (21.2–39.6) 0.502
 Yes 21.8 (16.1–28.4) 22.5 (15.1–31.4) 0.886 41.3 (35.7–47.1) 30.0 (23.4–37.3) 0.013
Time per day with the backpack on
 Less than half an hour 17.6 (13.0–23.0) 15.6 (10.0–22.7) 0.620 28.7 (23.0–34.9) 23.7 (17.6–30.8) 0.258
 More than half an hour 30.5 (24.2–37.4) 33.6 (24.9–43.3) 0.570 48.9 (42.3–55.6) 39.6 (30.5–49.4) 0.107
Walking to school
 No 24.1 (19.3–29.4) 20.0 (14.4–26.6) 0.303 37.1 (31.7–42.7) 28.5 (22.5–35.2) 0.043
 Yes 22.2 (15.7–29.9) 32.4 (21.8–44.6) 0.108 41.8 (34.0–49.9) 33.8 (23.4–45.5) 0.238
Performs sports regularly
 No 28.4 (21.3–36.4) 23.4 (14.5–34.4) 0.421 35.8 (30.5–41.5) 27.7 (21.4–34.6) 0.060
 Yes 21.0 (16.4–26.1) 23.6 (17.5–30.6) 0.512 44.1 (36.3–52.1) 34.4 (25.0–44.8) 0.124
Time per day watching TV
 Less than 1 h 28.1 (21.3–35.8) 23.3 (15.9–32.0) 0.365 45.1 (37.3–53.1) 33.6 (25.0–43.1) 0.057
 More than 1 h 20.8 (16.2–26.0) 23.7 (16.8–31.8) 0.500 35.3 (29.9–40.9) 27.5 (21.0–34.8) 0.081
Time per day on the laptop or video games
 Less than 1 h 23.0 (18.5–28.1) 21.3 (15.2–28.4) 0.660 37.9 (33.0–43.1) 31.5 (25.2–38.4) 0.127
 More than 1 h 24.6 (17.3–33.2) 27.5 (18.6–37.8) 0.634 41.7 (31.7–52.2) 25.9 (16.8–36.9) 0.028
Time per day studying
 Less than 2 h 23.8 (19.1–29.0) 20.9 (15.2–27.6) 0.471 38.0 (31.9–44.5) 27.8 (20.8–35.7) 0.038
 More than 2 h 22.8 (16.0–30.8) 29.7 (19.7–41.5) 0.269 39.4 (33.0–46.1) 32.3 (24.5–41.0) 0.181
Back lesion
 No 20.1 (16.2–24.3) 20.9 (15.9–26.7) 0.788 31.8 (27.2–36.6) 24.9 (19.7–30.8) 0.061
 Yes 57.5 (40.9–73.0) 58.8 (32.9–81.6) 0.926 81.5 (70.0–90.1) 65.7 (47.8–80.9) 0.077
  1. Comparison between control and intervention groups