Body mass index and smoking: cross-sectional study of a representative sample of adolescents in Denmark

To quantify the association between body mass index (BMI) and smoking (at all and daily smoking) stratified by gender, family social class, and ethnicity among adolescents aged between 13 and 15.

The analyses were based on the Danish contribution to the international Health Behaviour in School-aged Children survey in 2002 with self-reported data on height, weight, and smoking behaviour. The study population comprised 3,072 students aged between 13 and 15 (1,512 boys and 1,560 girls). Logistic regression analysis was used to quantify the association.

Odds of at all smoking by BMI (per step) was 1.10 (95% CI 1.03-1.17) among boys but there was no association among girls (OR 0.98, 95% CI 0.93-1.04). No significant association was found for daily smoking and BMI. The association between at all smoking and BMI (per step) was significant among boys of middle social class (OR 1.13, 95% CI 1.03-1.24) and Danish ethnicity (OR 1.10, 95% CI 1.02-1.19).

Significant association exists between smoking and BMI among boys of Danish ethnicity and middle family social class only.