OBJECTIVES: Asthma is one of the representative diseases that can cause a systemic inflammatory response. Anemia of chronic disease (ACD), also called anemia of inflammation, is known to be caused by diseases with a chronic inflammatory state. Whether the incidence of anemia is higher in asthmatic patients than in healthy control remains unclear. Thus, the objective of this study was to determine incidence of anemia in asthmatic patients and healthy adults.

METHODS: This was a retrospective cohort study using data from Seoul National University Hospital and Seoul National University Hospital Healthcare System Gangnam Center from 2008 to 2021. Patients with confounding diseases that might increase the risk of anemia before the first visit (index date) were excluded. The risk of anemia in asthma patients and healthy adults was then evaluated. A Cox regression model adjusting for patient age, gender, and obesity was used to compare anemia incidence between asthma patients and healthy adults.

RESULTS: A total of 3,085 patients were included in this study. Compared with healthy adults, the hazard ratio calculated after adjusting for patient's age, gender, and obesity as covariates for the incidence of anemia in asthma patients was 4.06 (95% CI: 2.70-6.09). Anemia occurred in 122 of 1,009 asthma patients aged 18 to 65 years and in 76 of 1,657 healthy adults. In elderly patients aged over 65 years, the rate ratio was analyzed to be 4.68, higher than that in relatively young adults. The adjusted HR was 5.56 (95% CI: 1.31-23.67).

CONCLUSIONS: The risk of anemia is increased in asthma patients after adjusting for patient's gender, age, and obesity and excluding effects of other risk diseases on anemia. Results of this study might provide evidence that asthma patients need regular anemia-related tests.