School performance and weight status of children and young adolescents in a transitional society in Thailand

OBJECTIVE: To study the association between current or previous weight status and school performance among children and young adolescents of Hat Yai municipality, southern Thailand.

DESIGN: Cross-sectional and longitudinal study

SETTING: Primary and secondary schools of Hat Yai municipality, southern Thailand.

SUBJECTS: 1207 grades 3–6 and 587 grades 7–9 students.

MEASUREMENTS: Body mass index (BMI, kg/m²) calculated from weight and height measurement of subjects in 1992 and 1994; parental education level and occupation, and monthly income, by questionnaire performed in 1992; grade-point-average (GPA) and grades of mathematics and Thai language from the school records of final examinations in 1994.

RESULTS: Overweight subjects (BMI value >85th percentile of the NHANES-I data for age and gender) in grades 7–9 had a mean GPA 0.20 point (95% confidence internal (CI)=0.04, 0.37) lower than that of the normal weight children after controlling for gender, age, school and grade. They were twice more likely to have low grades (lower than 2 on the scales of 0–4) of mathematics and Thai language than normal weight children. There were no associations between GPA or individual subject grades and previous BMI status in 1992. Children in grades 7–9 who became overweight over the two years, had a mean GPA of 0.48 point lower than those who did not become overweight (95% CI=0.12, 0.84). In grades 3–6 subjects, however, becoming overweight had no effect on GPA and individual subject scores.

CONCLUSIONS: Our study showed that being overweight and becoming overweight during adolescence (grades 7–9) was associated with poor school performance, whereas such an association did not exist in children (grades 3–6).