Association of exposure to secondhand smoke at home with early age at menarche in South Korea.

Abstract Objectives The secular trend in age at menarche (AAM) has declined both worldwide and in Korea. Early AAM is associated with the risk of several diseases, reproductive capacity, and psychological problems. We aimed to investigate the relationship between secondhand smoke (SHS) exposure at home and early puberty onset using AAM in Korean adolescents. Study design This is a retrospective cross-sectional study. Methods This study used data from the Korea Youth Risk Behavior Web-based Survey 2014–2015. We used the mean AAM (12.2 years) as a determinant of early AAM. After the exclusion of girls without menarche or who did not respond, the total population comprised 63,618 participants. We categorized AAM as ‘early’ and ‘average or late.’ Adolescents with SHS exposure were assigned to the ‘never exposed,’ ‘light exposure,’ and ‘heavy exposure’ groups. Multiple logistic regression analyses were performed. Results We observed a positive association, approximately 1.12 times, between early AAM and high SHS exposure (odds ratio [OR], 1.12; 95% confidence interval [CI], 1.05–1.19). Girls who started smoking before the age of 12 years (OR, 1.68; 95% CI, 1.41–1.99) showed a stronger association with early AAM than non-smokers. Active smoking showed a stronger association with early AAM. Never smokers with high SHS exposure at home were 1.13 times likelier to have an early AAM (OR, 1.13; 95% CI, 1.05–1.22) than those without SHS exposure. Conclusions In addition to active smoking, SHS may also be a risk factor for early AAM. Education aimed at active and secondhand smoking prevention is needed to protect children against early AAM.