Journal of Shandong University (Health Sciences) ›› 2024, Vol. 62 ›› Issue (1): 102-110.doi: 10.6040/j.issn.1671-7554.0.2023.0983

• Public Health & Management Sciences • Previous Articles     Next Articles

Mediators or confounders: should obesity be adjusted to estimate the effects of trihalomethanes on thyroid function

FAN Jiaxu1, CHENG Fang1, QIAO Junpeng1, FEI Haicheng1, CHEN Xueyu1, ZHAO Yun2, JIA Hongying3,4   

  1. 1. Department of Biostatistics, School of Public Health, Shandong University, Jinan 250012, Shandong, China;
    2. Licheng District Center for Disease Control and Prevention, Jinan 250100, Shandong, China;
    3. The Second Hospital, Shandong University, Jinan 250033, Shandong, China;
    4. Shenzhen Institute of Shandong University, Shenzhen 518057, Guangdong, China
  • Published:2024-02-02

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Abstract: Objective To explore whether obesity plays a confounding or mediating role in the effects of trihalomethanes on thyroid function. Methods The cross-sectional data were obtained from the NHANES database. The continuous and categorical variables were compared with weighted rank sum test and χ2 tests, respectively. Variables with skewed distribution were subjected to natural ln transformation; THM was classified according to the quartile distribution of ln transformed concentration; directed acyclic graphs(DAGs)and Logistic regression were introduced to explore the potential role of body mass index(BMI)in the causal pathway of THM exposure and thyroid function. Results There was no significant effect on the association between THM exposure and thyroid function before and after additional adjustment for BMI as a categorical variable; however, when stratified analyses were performed based on obesity, THM was a risk factor for elevated TSH levels in obese patients. Conclusion Considering collider bias, the potential heterogeneity observed in stratified analyses of obesity needs to be interpreted with caution, as well as the need for additional analyses of obesity as a confounder and/or mediator in THM studies.

Key words: Mediating effects, Confounders, Directed acyclic graph, Trihalomethanes, Obesity

CLC Number: 

  • Q451
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