Non‐anemic iron deficiency and symptoms of fatigue and insomnia in 59,668 Danish blood donors: Results from the Danish Blood Donor Study

BACKGROUND: Blood donation causes iron loss and increases the risk of non-anemic iron deficiency (NAID), which is not detected by hemoglobin screening alone. Evidence linking NAID to fatigue and insomnia symptoms in healthy blood donors remains limited and inconsistent. We aimed to investigate these associations in a large cohort of Danish blood donors. STUDY DESIGN AND METHODS: This cross-sectional study used data from the Danish Blood Donor Study collected from May 2015 to January 2025. Donors with both a ferritin measurement and questionnaire data on fatigue and insomnia within 90 days of the measurement were included. NAID was defined as ferritin <15 μg/L with normal hemoglobin level. Sex-stratified multivariable logistic regression models were adjusted for age, body mass index, smoking status, region, and donation history. Ferritin was also modeled continuously using linear spline regression. RESULTS: Among 59,668 donors, NAID was present in 9.5% of women and 2.0% of men. NAID was associated with fatigue among women (OR 1.22, 95% CI 1.06-1.40) and insomnia symptoms among men (OR 1.26, 95% CI 1.03-1.53). Continuous analyses suggested that lower ferritin concentrations were associated with higher odds of fatigue in both sexes and higher odds of insomnia symptoms in men. CONCLUSION: Low iron stores in non-anemic blood donors were associated with fatigue in women and insomnia symptoms in men. These findings suggest that hemoglobin screening alone may be insufficient to identify donors with symptomatic iron depletion and support consideration of ferritin monitoring as part of donor health strategies.