Impact of exposure to secondhand smoke on the risk of obesity in early adolescence

BACKGROUND: Exposure to secondhand smoke (SHS) might be associated with obesity in children. This study aimed to evaluate whether continuous, quit, or start exposure to SHS was associated with obesity risk in early adolescents. METHODS: We used population-based longitudinal data of primary school students in Adachi City, Tokyo, Japan, in 2018 (4th grade) and 2020 (6th grade) and studied 3605 students. The association between continuous, quit, start, or never exposed to SHS from 4th to 6th grade and BMI categories (underweight or normal weight, overweight, obesity) in 6th grade was investigated using ordinal logistic regression models. RESULTS: Continuous SHS group showed a higher risk of being in the high BMI category than no SHS group (OR = 1.51, 95% CI 1.16–1.96). The stratified analyses by sex showed a similar association in boys (OR = 1.74, 95% CI 1.25–2.44) but not in girls (OR = 1.14, 95% CI 0.74–1.76). Quitting SHS group did not show a higher risk of being in the high BMI category than no SHS group (OR = 1.11, 95% CI 0.75–1.66) and the same was true for boys (OR 1.46, 95% CI 0.88–2.41). CONCLUSIONS: Continuous SHS was a risk factor for obesity in boys in early adolescence; however, quitting SHS may help prevent it. IMPACT: Continuous secondhand smoke (SHS) was not associated with a higher risk of obesity in early adolescence in girls. Continuous SHS can be a risk factor for obesity in early adolescence in boys. Quitting SHS may help to prevent obesity in early adolescence in boys.