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News Author: Laurie Barclay, MD
Medscape Review Release Date: November 11, 2005
Original publication: Arch Pediatr Adolesc Med. 2005;159:1038-1042
Nov. 11, 2005 — Prolonged bottle-feeding is a risk for iron deficiency, as is Mexican-American descent, according to results from the National Health and Nutrition Examination Survey (NHANES III) reported in the November issue of the Archives of Pediatrics & Adolescent Medicine.
"This is the first study that we are aware of to report an association between prolonged bottle feeding and iron deficiency among a nationally representative sample of children one to three years of age," lead author Jane Brotanek, MD, MPH, from the Medical College of Wisconsin in Milwaukee, said in a news release. "Our data suggest that prolonged bottle-feeding among Mexican-American infants may be at least partly responsible for the high prevalence of iron deficiency seen in this group."
NHANES III included data on the feeding habits of 2,121 black, white, and Mexican-American toddlers aged one to three years, as well as measures of iron status, including transferrin saturation, free erythrocyte protoporphyrin, and serum ferritin. The investigators used bivariate and multivariate analyses to examine the association between bottle-feeding duration and iron deficiency.
"Toddlers who are bottle-fed consume large volumes of non–iron-fortified milk," Dr. Brotanek says. "This results in gastrointestinal blood loss together with a displacement of iron-rich foods from the diet."
At 24 to 48 months of age, 36.8% of Mexican-American children were still bottle-fed, as were 16.9% of white and 13.8% of black children. Multivariate analyses revealed that bottle-feeding for 24 to 48 months, and Mexican ethnicity were each associated with iron deficiency (odds ratio [OR], 2.8; 95% confidence interval [CI], 1.3 - 6.0; and OR, 2.9; 95% CI, 1.5 - 5.6, respectively).
The authors conclude that children with prolonged bottle-feeding and those of Mexican-American descent are at higher risk for iron deficiency, and they recommend targeting screening practices and nutritional counseling at these high-risk groups.
Study limitations include lack of data concerning use of iron-fortified formulas and the volume of milk and various iron-rich foods consumed; cross-sectional design limiting inferences of causality; sample sizes too small to perform analyses of other Latino subgroups; and use of data from NHANES III, which are now relatively old.
"Parents need to be aware that prolonged bottle-feeding and giving large volumes of milk to children older than 12 months can lead to problems with learning and development," Dr. Brotanek concludes. "Pediatricians need to counsel parents about feeding issues during the first year of life and encourage them to wean children from bottle-feeding by 15 months."
The National Research Service Award Program has disclosed that it supported this study.
Learning Objectives
· Describe the association between prolonged bottle-feeding and iron deficiency in children ages one to three years.
· Describe ethnic disparities in the risk for iron deficiency in children ages one to three years.
Clinical Context
The most common cause of anemia in infants is iron deficiency, which is associated with developmental delays and behavioral changes. Even in iron deficiency without anemia, the amounts of iron in the central nervous system decreases and can affect behavior. Looker and colleagues, in a study published in the March 26, 1997, issue of JAMA, report a 3% prevalence of iron-deficiency anemia and 9% prevalence of iron deficiency in children ages one to three years in the U.S. based on the 1988-1994 NHANES III.
One cause of iron deficiency is excessive cow's milk ingestion, which displaces consumption of adequate iron-rich foods in the diet and increases gastrointestinal blood loss, according to the American Academy of Pediatrics Committee on Nutrition. In turn, excessive cow's milk ingestion is associated with prolonged bottle-feeding. According to the American Academy of Pediatrics, infants should be weaned from the bottle by 15 months of age. A study by Lampe and Velez, published in the October 1997 issue of Clinical Pediatrics, reports that 18-month-old toddlers who were bottle-fed drank more cow's milk than non–bottle-fed toddlers. Kaste and Gift, in a study published in the July 1995 issue of the Archives of Pediatrics & Adolescent Medicine, found that 8% of children ages two to five years in the U.S. are bottle-fed and that prolonged bottle-feeding is associated with Latino ethnicity, poverty status, urban residence, and low parental location. A study by Bonuck and Kahn, published in the October 2002 issue of Clinical Pediatrics, report preliminary results of a small study of 95 children ages 18 to 56 months in an urban setting in which bottle-feeding was associated with weight-for-height status and with iron-deficiency anemia: 25% of bottle-fed children had anemia vs 15% of non–bottle-fed children.
The current study used data from the National Center for Health Statistics NHANES III to evaluate (1) the association between prolonged bottle-feeding and iron deficiency in children one to three years of age and (2) the association between Mexican-American children and prolonged bottle-feeding and iron deficiency.
Study Highlights
· Data for 2,121 children ages 1 to 3 years were obtained using NHANES III data from 1988-1994 on 33,994 subjects at least 2 months of age in the U.S. Also, various Spanish and English data tools were used for data collection. Variables included age, sex, poverty status (below federal threshold vs at or above threshold), ethnicity (non-Hispanic white, non-Hispanic black, Mexican American), caretaker education level, weight-for-height status, birth weight, blood lead level, and age of discontinuation of breast- or formula-feeding.
· Iron deficiency was diagnosed by 2 of 3 following abnormal values: transferrin saturation (<10% for ages 1 to 2 years and <12% for age 3 years); free erythrocyte protoporphyrin (>1.42 µmol/L for ages 1 to 2 years and >1.24 µmol/L for age 3 years); and serum ferritin (<10 µg/L).
· The prevalence of iron deficiency was 9%. Iron deficiency was more prevalent among Mexican-American children (16.9%) than white children (5.7%) or black children (8%); (P < .001). Iron deficiency was more prevalent among 1-year-old children (16.4%) than 2-year-olds (5.6%) or 3-year-olds (5.9%; P < .001). Iron deficiency was more prevalent with longer duration of bottle-feeding for 24 to 48 months (12.4%) and for 13 to 23 months (11.5%) than for 12 months or less (3.8%; P < .001). Iron deficiency was more prevalent for children with both risk factors of Mexican-American ethnicity and bottle-feeding more than 12 months (18.5%) vs children with neither risk factor (3.3%); P value not reported.
· There was no significant association between iron deficiency prevalence and sex, poverty status, caretaker education level, weight-for-height status, birth weight, lead level, or age at discontinuation of breast- or formula-feeding.
· The prevalence of iron-deficiency anemia was 2.6%. Iron-deficiency anemia was significantly associated with nonwhite ethnicity, younger children, longer bottle-feeding duration, poverty, lower caretaker education level, and low birth weight (<2,500 g). There was no significant association between iron-deficiency anemia and sex, weight-for-height status, lead level, and age at discontinuation of breast- or formula-feeding.
· Analysis of bottle-feeding duration by ethnicity showed that at 24 to 48 months more Mexican-American children were still bottle-fed (36.8%) vs white (16.9%) and black children (13.8%; P < .001).
· Multivariate analysis showed that bottle-feeding for 24 to 48 months and Mexican-American ethnicity were associated with greater adjusted odds of iron deficiency. Children bottle-fed for 24 to 48 months were 2.8 times more likely to be iron deficient vs children bottle-fed for 12 months or less (OR, 2.8; 95% CI, 1.3 - 6.0). Mexican-American children were 2.9 times more likely to be iron deficient vs white children (OR, 2.9; 95% CI, 1.5 - 5.6).
· Authors note the following limitations: NHANES III is a cross-sectional survey rather than a longitudinal survey; specific dietary information regarding quantities of milk or iron-rich foods is not available; small sample sizes precluded analyses of Latino subgroups; and NHANES III data is relatively old.
Pearls for Practice
· Iron deficiency prevalence is associated with increasing duration of bottle-feeding beyond 12 months of age; children bottle-fed for 24 to 48 months are almost three times more likely to be iron deficient.
· Mexican-American children have a higher prevalence of prolonged bottle feeding for 24 to 48 months than white and black children and are approximately three times more likely to be iron deficient than white children.