Demographic and toxic correlates of iron status in US women and children

Objective: To describe transferrin-receptor/ferritin ratio (TfR/F), ferritin, hemoglobin and mean corpuscular hemoglobin concentration values in a national representative sample of women and children, as well as to assess selected demographic and lead and cadmium level correlates for the TfR/F ratio. Methods: Cross sectional 2007-2008 US NHANES data were analyzed among 667 1-5 year old children and 1819 women aged 12-49 years. The TfR/F ratio was computed as TfR/log ferritin. TfR/F values (means and geometric means with 95% CI) were obtained by gender, age and race. Demographic and lead and cadmium levels were regressed on TfR/F using linear regression to obtain beta coefficients with 95% confidence intervals, accounting for survey weights and cluster sampling. Results: White women, but not children, had a lower TfR/F ratio than Mexican American women (β: -0.24, p<0.005). Negative correlation was seen between hemoglobin (g/dL) and TfR/F ratio levels in children (β: -0.16, 95% CI -0.28, -0.03) and women (β: -0.66, 95% CI -0.84, -0.48). Multivariate analyses showed that after adjusting for race, age, BMI, hemoglobin and C-reactive protein levels, significant associations were found between TfR/F and lead (β: 0.31, 95% CI 0.13, 0.49) and cadmium levels (β:0.39, 95% CI 0.25, 0.54) in 12-49 year old women. BMI was a significant correlate in children. TfR/R levels are useful markers of anemia and are related to exposure to toxic lead and cadmium levels, signaling possible effects of these toxics on hematopoiesis. Potential interactions by age and clinical implications are discussed.