PURPOSE Asthma can cause a systemic inflammatory response, and anemia of chronic disease (ACD) is known to be caused by other disorders with a chronic inflammatory state. However, it is unclear whether the incidence of anemia is increased in patients with asthma. The objective of this study was to compare the incidence of anemia in patients with asthma and healthy adults.

PATIENTS AND METHODS This retrospective cohort study included patients newly diagnosed with asthma at Seoul National University Hospital from 2010 to 2017. Patients with comorbidities before the first visit (index date) that may increase anemia risk were excluded. Cox regression models adjusting for patient age, sex, and obesity were used to compare anemia hazard ratios (HRs) between asthma patients (n=1354) and healthy adults (n=1731).

RESULTS This study included 3085 patients. During 5-y follow-up, anemia occurred in 203 (15.0%) patients with asthma and 79 (4.6%) healthy adults. Compared with healthy adults, the HR for anemia after adjusting for age, sex, and obesity was 4.06 (95% CI: 2.70-6.09) in patients with asthma. In patients aged 18-64.9 y, the adjusted HR of anemia was 3.27 (95% CI: 2.12-5.04) in patients with asthma, compared to healthy patients. In patients >65 y, this adjusted HR was 5.56 (95% CI: 1.31-23.67).

CONCLUSION The risk of anemia was increased in patients with asthma after adjusting for sex, age, and obesity and excluding comorbidities that can cause anemia. These results suggest the need for regular monitoring for anemia in patients with asthma.