Association between the C-reactive protein to albumin ratio with asthma and mortality in adult: a population-based study

Asthma is a prevalent chronic disease characterized by airflow obstruction, causing breathing difficulties and wheezing. This study investigates the association between the C-reactive protein to albumin ratio (CAR) and asthma prevalence, as well as all-cause and respiratory mortality among asthma patients, using data from the 2001-2018 National Health and Nutrition Examination Survey. We included participants aged 20 years and older with complete CAR data, excluding those who were pregnant or lost to follow-up. The analysis employed weighted logistic regression and Cox proportional hazards models with stepwise adjustment, restricted cubic spline analysis for nonlinear relationships, and time-dependent ROC curves for predictive accuracy. Results showed that the highest CAR quartile significantly increased the risk of asthma (OR 1.56, 95% CI 1.38-1.78), all-cause mortality (HR 2.20, 95% CI 1.67-2.89), and respiratory mortality (HR 2.56, 95% CI 1.30-5.38). The impact of CAR on all-cause mortality was particularly significant in hypertensive patients. These findings highlight CAR's potential as a valuable biomarker for predicting asthma prevalence and mortality, underscoring its role in asthma management and prognostication.