Association between eosinophil number and overweight status: a nonlinear, bidirectional study.

BACKGROUND

The relationship between eosinophil number and overweight status (or obesity) remains a subject of debate. While animal studies suggest a negative correlation between the two, most clinical studies indicate a positive correlation. Therefore, we hypothesize that a nonlinear relationship may exist between eosinophil number and overweight status. This study aims to investigate the association between eosinophil number and overweight status (as well as related indicators) using data from the National Health and Nutrition Examination Survey (NHANES).

METHODS

We utilized data from NHANES 1999-2018, where eosinophil number was obtained from laboratory tests. Overweight status was defined as a body mass index (BMI) ≥ 25. We then applied weighted logistic regression/linear regression, subgroup analysis, and restricted cubic splines (RCS) analysis to investigate the association between eosinophil number and overweight status (as well as related indicators).

RESULTS

A total of 77,217 individuals were included in this study, with 38,106 individuals in the non-overweight group (BMI < 25) and 39,111 individuals in the overweight group (overweight and obesity, BMI ≥ 25). The logistic regression analysis revealed a significant association between eosinophil number and overweight status (OR: 2.38, 95% CI: 1.81-3.12, P < 0.001). Additionally, eosinophil number was significantly positively correlated with obesity/BMI/triglycerides and negatively correlated with High-Density Lipoprotein (HDL). Finally, the nonlinear regression results indicated an inverted U-shaped relationship between eosinophil number and overweight status/obesity/BMI.

CONCLUSION

Our study demonstrates an inverted U-shaped relationship between eosinophil number and overweight status/obesity/BMI. Eosinophil number is also significantly associated with HDL and triglycerides. These findings suggest that eosinophils may play a role in overweight (or obesity) and provide valuable insights for exploring the underlying immune mechanisms of overweight status.