Abstract Rationale Asthma is a chronic inflammatory airway disorder influenced by pulmonary and systemic factors. Epidemiologic and experimental data suggest associations between asthma, anemia, and reduced iron stores. Sex may modify this relationship: females, with lower baseline iron reserves, menstrual blood loss, and hormone-mediated immune effects, may exhibit greater susceptibility, whereas males, with higher iron stores and androgen-related anti-inflammatory influences, appear less affected. This study tested the hypothesis that diminished iron stores, rather than anemia itself, are associated with asthma, and that this relationship differs by sex. Methods Data were analyzed from nine consecutive NHANES 2-year cycles (1999-2018), a nationally representative U.S. dataset. Lifetime asthma was defined as a prior physician diagnosis and active asthma as “Do you still have asthma?”. Anemia was defined by WHO criteria (hemoglobin 12 g/dL in females and 13 g/dL in males), and iron deficiency as ferritin 30 ng/mL. Accordingly, iron status was categorized as normal, iron deficiency anemia (IDA), iron deficiency without anemia (IDWA), and anemia without iron deficiency (AWID). Analyses followed NHANES guidelines and were conducted with the SURVEY package in R. Results Female participants were older and had lower eosinophil counts, ferritin, and hemoglobin levels, with a higher prevalence of anemia, lifetime asthma, and current asthma. Similar trends were observed among participants with available ferritin data (Table 1). In unadjusted analyses, ferritin levels were inversely associated with lifetime (β = -0.19; p 0.001) and active asthma (β = -0.35; p 0.001), but these associations were not significant after adjustment for sex, age, BMI, race, and log10-transformed eosinophil count (lifetime: β = 0.03; p = 0.61; active: β = -0.08; p = 0.40). In contrast, anemia was associated with increased odds of lifetime (adjusted OR 95% CI, 1.52 1.21-1.92) and active (1.50 1.13-1.99) asthma in males, but not in females (0.98 0.86-1.12 and 0.98 0.83-1.15, respectively). Among males, AWID was associated with active asthma (2.07 1.08-3.96), whereas IDA and IDWA were not. No associations were observed among females. Conclusion The relationship between anemia and asthma may be primarily driven by inflammation related to asthma rather than true iron deficiency. After adjustment, ferritin was not independently associated with asthma, whereas anemia—particularly AWID—remained associated among males. These findings suggest that asthma-associated systemic inflammation contributes to anemia of chronic disease, underscoring the need to distinguish inflammatory anemia from nutritional iron deficiency in research and clinical management. This abstract is funded by: NIH
Keswani et al. (Fri,) studied this question.