Unexplained decline in the prevalence of anemia among US children and women between 1988-1994 and 1999-2002.

BACKGROUND: The current anemia burden among US preschool children and women of childbearing age has not been documented.

OBJECTIVE: We used data from National Health and Nutrition Examination Surveys 1988-1994 and 1999-2002 to examine recent anemia changes.

DESIGN: We calculated the prevalence of anemia (hemoglobin < 11.0 g/dL at <24 mo, <11.1 g/dL at 24-59 mo, and <12.0 g/dL for women), iron deficiency anemia (anemia plus abnormal value >or=2: serum ferritin, transferrin saturation, and erythrocyte protoporphyrin), and high blood lead (>or=10 microg/dL) with anemia among children 12-59 mo and women 20-49 y in both surveys. Among women, we also calculated the prevalence of folate deficiency (erythrocyte folate < 317.2 nmol/L) with anemia and high C-reactive protein (>10 mg/L) with anemia. Multiple logistic regression was used to compare anemia prevalence between surveys, with control for race and age.

RESULTS: Anemia declined significantly in children (from 8.0% to 3.6%; OR: 0.4; 95% CI: 0.3, 0.7) and women (10.8% to 6.9%; OR: 0.6; CI: 0.4, 0.7), but the prevalence of iron deficiency anemia did not change significantly in children (1.5% compared with 1.2%; OR: 0.7; 95% CI: 0.4, 1.5) or women (4.9% compared with 4.1%; OR: 0.8; 95% CI: 0.6, 1.1). Folate deficiency with anemia declined significantly in women (from 4.1% to 0.5%; OR: 0.1; 95% CI: 0.1, 0.2), but logistic regression models and standardization indicated that none of the known possible anemia causes could account for the decline in total anemia in children or women.

CONCLUSIONS: The prevalence of anemia declined significantly among US women and children between 1988-1994 and 1999-2002, but this decline was not associated with changes in iron or folate deficiency, inflammation, or high blood lead.