Trends in Anemia and Iron Deficiency Among Nonpregnant U.S. Women of Reproductive Age, 1999–2023

OBJECTIVE: To evaluate temporal trends in the prevalence of anemia, iron deficiency, and iron deficiency anemia (IDA) among nonpregnant reproductive-aged women in the United States. METHODS: In this serial cross-sectional study of NHANES (National Health and Nutrition Examination Surveys) from 1999-2000 through 2021-2023, nonpregnant women aged 20-45 years were included. Hemoglobin and ferritin data were used to evaluate time trends in anemia (defined as a hemoglobin concentration less than 12.0 g/dL), iron deficiency (defined as a serum ferritin level less than 15.0 micrograms/L), and IDA (defined as a hemoglobin concentration less than 12 g/dL and a serum ferritin level less than 15.0 micrograms/L). RESULTS: A total of 8,200 U.S. nonpregnant reproductive-aged women were included in this analysis. The prevalence of anemia, iron deficiency, and IDA (weighted to the U.S. population) for the combined time periods was 9.8% (95% CI, 9.0-10.7%, 3.28 million), 17.3% (95% CI, 16.4-18.3%, 5.70 million), and 6.2% (95% CI, 5.5-6.8%, 2.03 million), respectively. The prevalence of anemia increased from 8.0% (95% CI, 5.8-10.9%) in 1999-2000 to 14.2% (95% CI, 11.8-17.1%) in 2021-2023. In contrast, there was a modest increase in the iron deficiency prevalence from 17.9% (95% CI, 16.4-19.5%) to 18.8% (95% CI, 16.1-21.9%). The IDA prevalence increased from 4.3% (95% CI, 3.2-6.0%) to 9.1% (95% CI, 7.3-11.4%). In adjusted logistic regression models with each NHANES survey cycle as a continuous variable, the odds of anemia and IDA each rose by approximately 8% per cycle (anemia: adjusted odds ratio [aOR] 1.08, 95% CI, 1.05-1.11; IDA: aOR 1.08, 95% CI, 1.04-1.12) between 1999 and 2023. CONCLUSION: In a population-based cohort of U.S. nonpregnant reproductive-aged women, the prevalence of anemia and IDA increased substantially between 1999-2000 and 2021-2023. The prevalence of iron deficiency remained high and showed no significant change over this period. Given that iron deficiency and anemia are important causes of disability, these findings may inform future screening policies for these conditions in nonpregnant reproductive-aged women.