Association between childhood atopic dermatitis, malnutrition, and low bone mineral density: A US population-based study

Background: Children with atopic dermatitis (AD) have multiple risk factors for low bone mineral density (BMD). Methods: We analyzed data from 3049 children and adolescents aged 8-19 yrs from the 2005-2006 National Health and Nutrition Examination Survey, including a cross-sectional questionnaire, dual energy X-ray absorptiometry, and blood samples. Results: In multivariate models that controlled for age, sex, race/ethnicity, level of education and household income, body mass index (BMI), and smoking in the household, AD was associated with lower BMD z-score for the total femur (survey linear regression; adjusted β [95% CI]: -0.42 [0.68, -0.16]), including trochanter (-0.29 [-0.54, -0.05]) and femoral neck (-0.29 [-0.53, -0.05]) and total lumbar spine (-0.31 [-0.52, -0.11]). Children with AD had higher median levels of serum IgE (110.0 vs. 53.0 kU/l), peripheral lymphocyte (2.9 vs. 2.5 × 10³ cells/μl), and eosinophil counts (0.3 vs. 0.2 × 10³ cells/μl) (Mann-Whitney U-test, p ≤ 0.003 for all), but not CRP levels (0.03 vs. 0.04 mg/dl) and higher odds of 25-OH vitamin D deficiency (survey logistic regression; odds ratio [OR] [95% CI]: 4.81 [1.21, 20.81]), low calcium (2.56 [1.24, 5.28]), low alkaline phosphatase (2.56 [1.20, 5.44]), and higher tertiles of LDH (tertile 2: 6.36 [1.75, 23.18]; tertile-3: 4.57 [1.32, 15.85]), but not parathyroid hormone (PTH) or albumin. Finally, children with AD had higher rates of low BMD, that is, BMD z-score <-2, of the femur (23.4% vs. 18.4%) and spine (35.3% vs. 24.5%). In multivariate logistic regression models of low BMD of femur and/or spine using stepwise selection of the 30 sociodemographic and clinical factors, laboratory values, and medications used, AD remained a significant covariate (1.33 [1.32-1.34]). The covariates with the largest effects on low BMD were low PTH and albumin, higher basophil count, Hispanic ethnicity, and BMI <5th percentile. Among children with AD, 56.2% of those with Hispanic origin, 52.8% with BMI <5th percentile, 75.0% with low albumin, and 54.0% with low PTH had low BMD. Conclusions: Children with AD have lower BMD, particularly those with malnutrition and Hispanic ethnicity.