Smoothed Urinary Iodine Percentiles for the US Population and Pregnant Women: National Health and Nutrition Examination Survey, 2001-2010

摘要

Background: Iodine intake is essential for normal growth, development and metabolism throughout life, especially for women during gestation and lactation. The present study applies a novel statistical approach, providing smoothed urinary iodine (Ul) percentile curves for the total US population as well as the categories of sex, race/ethnicity, women of childbearing age and pregnant women who were participants in the National Health and Nutrition Examination Survey (NHANES) 2001 -2010. To our knowledge, this is the first application of this technique to NHANES nutritional bio-marker data. Methods: We used Ul and urinary creatinine that were measured in participants aged 6 and older in the NHANES survey periods 2001 -2002,2003-2004,2005-2006, 2007-2008 and 2009-2010. A nonparametric double-kernel method was applied to smooth percentile curves for Ul and creatinine-corrected results. Results: The Ul population estimates showed a U-shaped distribution by age for the total US population. Overall, females had lower Ul concentrations and median values compared to males (median Ul for females, 141.8 mug/1; median Ul for males, 176.1 mug/l; p < 0.0001). Non-Hispanic blacks had the lowest median Ul concentrations compared to other racial/ethnic groups (p < 0.0001). Among women of childbearing age (15-44 years), Ul concentrations mostly declined with increasing age. Pregnant women aged 35 years and older tended to have higher Ul concentrations than younger pregnant women at similar percentiles. Conclusions: The smoothed reference distribution of Ul concentrations provides an improved and visual display of the entire distribution of values for the US population and specific demographic categories.