Association Between Atopic Disease and Anemia in US Children.

IMPORTANCE Atopic disease is associated with chronic inflammation, food allergen avoidance, and use of systemic immunosuppressant medications. All these factors have been shown to be associated with anemia. OBJECTIVE To investigate whether atopic disease is associated with increased risk of childhood anemia. DESIGN, SETTING, AND PARTICIPANTS A cross-sectional survey and laboratory assessment were conducted using data from the 1997-2013 US National Health Interview Survey (NHIS) that included 207,007 children and adolescents and the 1999-2012 National Health and Nutrition Examination Survey (NHANES) that included 30,673 children and adolescents. Analysis of the data was conducted between August 1, 2014, and August 28, 2015. EXPOSURES Caregiver-reported history of eczema, asthma, hay fever, and/or food allergy. MAIN OUTCOMES AND MEASURES Anemia was defined by caregiver report in the NHIS and by hemoglobin levels for age and sex in the NHANES. RESULTS Data were collected on 207,007 children and adolescents from NHIS, representing all pediatric age, sex, racial/ethnic, household educational level, and income groups. The US prevalence was 9.5% (95% CI, 9.4%-9.7%) from all years of the NHIS for health care-diagnosed eczema, 12.8% (95% CI, 12.6%-13.0%) for asthma, 17.1% (95% CI, 16.9%-17.3%) for hay fever, 4.2% (95% CI, 4.1%-4.3%) for food allergy, and 1.1% (95% CI, 1.1%-1.2%) for anemia. In multivariable logistic regression models controlling for age, sex, race/ethnicity, annual household income, highest educational level in the family, insurance coverage, number of persons in the household, birthplace in the United States, and history of asthma, hay fever, and food allergy, anemia was associated with eczema in 14 of 17 studies, asthma in 11, hay fever in 12, and food allergy in 12. In multivariable analysis across the NHIS (with results reported as adjusted odds ratios [95% CIs]), children with any eczema (1.83; 1.58-2.13), asthma (1.31; 1.14-1.51), hay fever (1.57; 1.36-1.81), and food allergy (2.08; 1.71-2.52) had higher odds of anemia (P < .001 for all). In the NHANES, current history of asthma (1.33; 1.04-1.70; P = .02) and eczema (1.93; 1.04-3.59; P = .04) were associated with higher odds of anemia, particularly microcytic anemia (asthma: 1.61; 1.09-2.38; P = .02; eczema: 2.03; 1.20-3.46; P = .009) while history of hay fever was not associated with anemia (0.85; 0.62-1.17; P = .33). CONCLUSIONS AND RELEVANCE The association between atopic disease and anemia was reproducible in multiple cohorts. Future studies are needed to identify the determinants of association between atopic disease and anemia.