The relationship between red blood cell distribution width and long-term prognosis of asthma: a population-based study

Statistically, 30% of asthma deaths occur among asthmatics with insignificant symptoms, which creates a social burden. We aimed to analyze the role of erythrocyte distribution width (RDW) in the prognosis of asthma, especially in patients with insignificant symptoms. We included 3039 adult (≥ 20 years) asthma patients from the National Health and Nutrition Examination Survey (NHANES). Cox regression was used to assess the association between RDW and long-term mortality. We adjusted three models to reduce potential bias. Subgroup analysis is used to evaluate specific populations. In addition, receiver operating characteristic (ROC) curves were used to analyze the predictive effect of RDW on asthma mortality. After a mean follow-up of 130 months, we found a positive correlation between RDW and long-term mortality. After aliquoting RDW into thirds, the high RDW (RDW ≥ 13.0%) group had higher all-cause mortality (HR 1.66, 95% CI 1.18-2.34) and respiratory mortality (HR 8.69, 95% CI 2.03-37.3). There was a significant interaction of RDW in the male and wheezing subgroups for respiratory mortality. Combining RDW and wheezing, we found that patients with high RDW and wheezing had the most increased respiratory mortality, and patients with high RDW but no wheezing also had higher mortality. Furthermore, the area under the curve of the RDW in predicting respiratory death in asthmatics was greater than 80%. Our study showed an association between high RDW and poor prognosis in asthma patients. In combination with wheezing symptoms, RDW is expected to be a biomarker for asthma management.