Association between Olympic Games and children's growth: evidence from China.

Objectives: To estimate the association between the 2008 Beijing Olympic Games (BOG) and growth of children in China.

Methods: A total sample of 6 951 children aged 3-10 years were included, among which 3 201 were interviewed in 2014 and 3 750 were interviewed in 2018. The BOG was used as a natural experiment. Exposure to the BOG was established by triple differences measured by age group, survey period and whether child participants were living in BOG areas or not, respectively. Children's growth was assessed by binary variables of stunting, underweight, overweight and obesity. The difference-in-difference-in-differences (DDD) method was used to estimate the association between the BOG and children's growth.

Results: DDD estimates showed that the BOG was significantly associated with decreased risks of children's underweight (OR 0.12; 95% CI 0.02 to 0.69) and overweight (OR 0.43; 95% CI 0.19 to 0.98) after controlling for multiple covariates in fractional polynomial models. There was significant sex heterogeneity with regard to the association between BOG and obesity, that is, lower odds of obesity (OR 0.24; 95% CI 0.06 to 0.94) were found in female children but not in male children.

Conclusion: The BOG was positively associated with healthier growth of children including decreased risks of both undernutrition and overnutrition. More attention should be given to the improvement of health surveillance and services before and after sporting events so that the active role of such mega-events in the lasting well-being of the public can be determined in more detail.