S-shaped association between hs-CRP/HDL-C index and overweight/obesity in children and adolescents: a population-based study.

BACKGROUND: Obesity has become a growing public health problem worldwide, especially in children and adolescents. The ultrasensitive C-reactive protein (hs-CRP)/high-density lipoprotein cholesterol (HDL-C) index is a widely recognized marker of metabolic disorders and inflammatory responses. However, its connection to overweight or obesity in children and adolescents remains unclear. This study aimed to examine the association between the hs-CRP/HDL-C index and overweight or obesity, to identify its possible threshold effect, and to offer a new theoretical basis for prevention and control among youth. METHODS: This study investigated the relationship between hs-CRP/HDL-C index and overweight and obesity in children and adolescents aged 6-19 years, utilizing data from the 2015-2020 National Health and Nutrition Examination Survey (NHANES). This analysis employed t tests, Chi-square tests, multiple logistic regression, restricted cubic spline regression (RCS), and piecewise regression methods to validate the association between the hs-CRP/HDL-C index and overweight/obesity, and to explore potential nonlinear patterns and key thresholds between the two. RESULTS: This study included 3853 children and adolescents. Multivariate logistic regression analysis revealed a significant positive relationship between the log-transformed indicator and overweight/obesity (OR = 5.81; 95% CI 5.02-6.75; P < 0.001). Furthermore, smoothed curve fitting revealed a nonlinear S-shaped dose-response relationship between the two variables. In addition, segmented regression analysis of hs-CRP/HDL-C identified two inflection points (0.653 and 1.593). Notably, except for household income, interaction p values across subgroups were all greater than 0.05, indicating high stability and consistency among subgroups. However, household income exerted a significant modifying effect. CONCLUSION: This study finds that the hs-CRP/HDL-C index is associated with overweight and obesity in children and adolescents in a manner that is not linear. There is a critical range (0.653-1.593) where higher values of the index are related to lower rates of overweight and obesity. Based on these results, it is recommended that pediatric healthcare providers use hs-CRP/HDL-C testing routinely, which may help identify children at risk and support early obesity prevention. Future studies should confirm these findings in additional groups and develop more effective interventions.