Associations of only-child status with health outcomes and risky behaviors in Korean middle- and high-school students: An outcome-wide analysis.

The proportion of children who are the only child in the family are increasing. Several associations between only-child status and health outcomes or risky behaviors have been identified, but no study has explored associations across a wide range of outcomes in a single study. We used the 2019 Korea Youth Risk Behavior Survey, a nationwide cross-sectional survey of 57,303 middle and high school students, to perform an outcome-wide analysis on six health outcomes and risky behaviors, i.e. alcohol use, asthma, body mass index, sexual activity, smoking, and suicide attempt. Individual multivariable logistic regression models examined associations between single-child status and each outcome or behavior. Of the eligible 38,211 students, 5,334 students (14.0 %) were the only child in their family, while 32,877 students (86.0 %) had siblings. Of the six selected outcomes and behaviors, alcohol use (aOR 0.88, 95 % CI 0.82-0.94), asthma (aOR 1.22, 95 % CI 1.10-1.35) and sexual activity (aOR 1.16, 95 % CI 1.02-1.31) were significantly associated with only-child status. Thus, being the only child among South Korean adolescents is both a potential protective factor and risk factor for different health outcomes and behaviors. Future research is warranted to corroborate these findings and identify mechanisms, which could provide evidence for reducing adverse outcomes and behaviors in adolescents.