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Table 3.

Univariate analysis of relationship demographic and school-related participant characteristics and self-reported presence of back pain (binary outcome).

Presence of back pain at least once a monthNo (%)Yes (%)p-value
GenderMale5545<0.01**
Female4060
No. of bags17030<0.01**
2+5941
Type of bagBackpack67330.01*
Other7426
How bag is carriedTwo shoulder6832<0.01**
One shoulder5644
Other6832
Sport participationYes68320.14
No6733
GradeGrade 57624<0.01**
Grade 67327
Grade 75743
Grade 85446
Grade 96832
School typePublic5545<0.01**
Non-public4555
Mean (SD)Mean (SD)p-value
BMI (kg/m2)19.9 (4.7)20.7 (4.9)<0.01**
Percentage bag weight to body weight13.7 (6.2)14.5 (6.3)<0.01**
Age (years)11.1 (1.4)11.5 (1.5)<0.01**
BMI: body mass index
CI: confidence interval
SD, standard deviation.

Chi-square and t-test analysis.
**p-value significant at <0.01
*p-value significant at <0.05.