Obesity Indicators and Female Asthma Risk: The Mediating Role of White Blood Cell Count Based on NHANES Data Analysis

Objective This study utilizes data from the National Health and Nutrition Examination Survey (NHANES) conducted between 2009 and 2018 to investigate the associations between obesity indicators (BMI and BRI), the inflammatory marker (WBC), and asthma in women. Additionally, the study explores the potential mediating role of WBC in the relationship between BMI, BRI, and asthma. Methods This A total of 3,792 eligible female participants were included in this cross-sectional study. We applied various statistical methods, including logistic regression, restricted cubic spline (RCS), generalized additive model (GAM), and mediation analysis, to assess the relationships between BMI, BRI, WBC, and asthma in women. Results The weighted analysis revealed that asthma patients had significantly higher levels of BMI, BRI, and WBC compared to non-asthmatic individuals (all P < 0.001). In unadjusted logistic regression models, these indicators were significantly associated with asthma, and the associations remained significant after adjusting for potential confounders. Quartile-based analysis showed that participants in the highest quartile (Q4) for BMI, BRI, and WBC exhibited a significantly increased risk of asthma. RCS analysis further supported the nonlinear relationships between BMI, BRI, WBC, and asthma, while mediation analysis demonstrated that WBC acted as a significant mediator in the relationship between BMI/BRI and asthma. Conclusion This study identifies significant and nonlinear associations between BMI, BRI, and WBC with the risk of asthma in women. Moreover, WBC was found to partially mediate the effects of BMI and BRI on asthma, offering new insights into the inflammatory mechanisms underlying obesity-related asthma in females.