Association between the C-reactive protein-triglyceride-glucose index and asthma risk: evidence from the NHANES cohort and validation in the CHNS cohort

• CTI correlates with increased asthma risk in NHANES and CHNS cohorts. • No nonlinear relationship found between CTI and asthma risk. • CTI integrates inflammation and metabolism for asthma risk assessment. Asthma is a chronic respiratory disorder characterized by airway inflammation and reversible airflow limitation. Emerging evidence highlights the roles of systemic inflammation and metabolic dysregulation in its pathogenesis. The C-reactive protein-Triglyceride glucose Index (CTI), a novel composite biomarker integrating inflammatory and metabolic components, may reflect these processes, yet its association with asthma remains unclear. Data from 18,579 adults in the National Health and Nutrition Examination Survey (NHANES, 1999–2010, 2015–2018) were analyzed to examine the relationship between CTI and asthma prevalence. Logistic regression models with progressive adjustments for demographic, lifestyle, and clinical covariates were applied. Nonlinear and threshold relationships were evaluated using restricted cubic splines. The authors performed subgroup analyses in participants with metabolically unhealthy obesity and in never-smokers, and conducted a brief association validation using data from the China Health and Nutrition Survey (CHNS) 2009 ( n = 6220). In NHANES, each unit increase in CTI was associated with a 20 % higher asthma likelihood after full adjustment (OR = 1.20, 95 % CI: 1.04–1.40, p = 0.018). Subgroup analyses indicated that the positive association remained robust among participants with metabolically unhealthy obesity and never-smokers. The association appeared linear, with no evidence of a significant threshold effect. The CHNS cohort confirmed the positive association (OR = 1.61, 95 % CI: 1.11–2.31, p = 0.012). A stable positive association was observed between CTI and asthma, suggesting that CTI may serve as a convenient biomarker for risk assessment; however, longitudinal studies are warranted for further validation.