A cross-sectional study reveals high prevalence rates of both absolute and functional iron deficiency among U.S. adults, including those without traditional risk factors.
The study, published in JAMA Network Open, estimates that 14% of U.S. adults had absolute iron deficiency, defined as serum ferritin less than 30 ng/mL regardless of transferrin saturation, while 15% had functional iron deficiency, characterized by serum ferritin greater than or equal to 30 ng/mL with transferrin saturation less than 20%.
The study finds women younger than 50 years had the highest prevalence of absolute iron deficiency at 34%. Among men, the prevalence of absolute iron deficiency was highest in those older than 65 years. Functional iron deficiency was more common than absolute iron deficiency in all age and sex categories except women younger than 50 years.
In fully adjusted multinomial regression models, the relative risk (RR) of absolute iron deficiency vs iron-replete status was significantly higher among women compared with men younger than 50 years of age. Similar results were obtained for the risk of functional iron deficiency vs iron replete status for women younger than 50 years compared with men younger than 50 years and women aged 50 years or older compared with men younger than 50 years.
Iron supplement use ranged from 22% to 35% among women with iron deficiency and from 12% to 18% among men with iron deficiency, depending on age.
Higher body mass index was associated with higher serum ferritin levels but lower transferrin saturation. Individuals with anemia, heart failure, chronic kidney disease, or current pregnancy were more likely to have absolute, but not functional, iron deficiency than those without such conditions. Among adults without anemia, heart failure, chronic kidney disease, or current pregnancy, the estimated prevalence of absolute iron deficiency was 11%, and functional iron deficiency was 15%.
Dietary iron intake, alcohol use, and food security were not associated with absolute or functional iron deficiency. Marginal food security, but not low or very low food security, was significantly associated with lower dietary iron intake.
The research analyzed data from 8,021 participants in the National Health and Nutritional Examination Survey 2017-2020 prepandemic cycle. The study included noninstitutionalized, civilian women and men aged 18 years or older who had available serum ferritin, iron, and unsaturated iron binding capacity measurements. The prevalence of absolute and functional iron deficiency was estimated among all adults in the U.S. and separately among women and men according to age category (>18 years to <50 years, 50-65 years, and ≥65 years) using recommended sample weights and sampling design factors to provide estimates representative of the national, noninstitutionalized civilian population.
One study investigator reported receiving grants from the NIH to her institution outside the submitted work. Another reported receiving speaking fees from ASHP Advantage and consulting fees from Kiniksa Pharmaceuticals, LLC, outside the submitted work. No other disclosures were reported.