The relationship between secondhand smoke exposure in Chinese children and adolescents and renal function and hyperuricemia: a cross-sectional study.

Background and objectives: Exposure to second-hand smoke (SHS) can potentially influence serum uric acid levels. However, there remains a relative paucity of studies on this topic among children and adolescents. This study intends to examine the association between SHS exposure and hyperuricemia (HUA) among Chinese children and adolescents, and to explore the potential mediating role of renal function in this relationship. Methods: The data for this cross-sectional study were sourced from the "Health Monitoring of Chinese Children and Lactating Women Nutrition and Health Surveillance" (CCLWNHS) carried out between 2016 and 2018. It encompassed a total of 13,062 individuals aged 6-17 from four provinces, comprising 6,536 boys and 6,526 girls. The frequency of the research subjects' exposure to SHS was acquired via a questionnaire survey. The dietary intake was collected through a 3-day 24-hour dietary retrospective questionnaire. Blood samples were gathered, and indicators such as uric acid and serum creatinine were examined. The prevalence of HUA is defined according to the fasting serum uric acid level, and the threshold differs according to age and gender. The function of the kidneys is assessed using the glomerular filtration rate (eGFR). The Chi-square test, Pearson correlation test, and logistic regression were employed to examine the associations among SHS, HUA, and eGFR. The LASSO model was utilized to select variables, and the XGBoost model was employed to forecast the occurrence of HUA. The mediation effect and Sobel test were utilized to analyze the effect of eGFR on SHS and HUA. Result: The prevalence rate of HUA among children and adolescents aged 6-17 stands at 20.5%. The exposure rate of SHS in the study population was found to be 41%. When compared with daily exposure to SHS, no exposure to SHS emerged as a protective factor for HUA (OR = 0.811, 95% CI: 0.698, 0.943). The results of the stratified analysis indicated that, in comparison to boys exposed to SHS on a daily basis, boys not exposed to SHS were identified as a protective factor for HUA (OR = 0.747, 95% CI: 0.613, 0.911). Mediation analysis demonstrated that eGFR mediated 10.42% of the association between SHS and HUA in boys. Furthermore, the mediating effect of eGFR on the relationship between SHS exposure and HUA in boys aged 12-17 reached 100%. Conclusion: Exposure of children and adolescents, particularly boys, to SHS may elevate the incidence of HUA by impairing the glomerular filtration function. Therefore, it is imperative to enforce the smoking ban in public places more stringently.