The association of overweight with allergy and asthma in children: Findings from the National Health and Nutrition Examination Survey (NHANES) 1999--2006

Obesity and asthma prevalence have both risen among children over the last several decades, and research efforts increasingly suggest that obesity is associated with asthma. Atopy is a strong risk factor for asthma, but previous literature on the relationship between obesity and atopy has been inconsistent. In addition, some, but not all, studies have shown that the effect of obesity on asthma is stronger among non-atopic individuals than among those with atopy. Systemic inflammation may be a factor in the relationship between obesity and asthma. Breastfeeding may potentially protect against obesity, atopy, and asthma.;This dissertation used National Health and Nutrition Examination and Survey (NHANES) data from 1999-2006 to examine the relationship between obesity and asthma among U.S. children age 2-19. Data from 2005-2006, which include assays for total and allergen-specific IgE, were used to explore the relationship of obesity with IgE levels, atopy, and allergy symptoms, and also to stratify the obesity-asthma analysis by atopic status. The protective effect of breastfeeding was investigated using data for children age 1-6.;Obese children were more likely to report having current asthma than children of normal weight (OR: 1.68, 95% CI: 1.33, 2.12). The association did not differ by gender, but was stronger among non-atopic children than among children with at least 1 positive specific IgE result (OR: 2.46, 95% CI: 1.21, 5.02 vs. OR: 1.34, 95% CI: 0.70, 2.57; interaction p-value 0.09). Total IgE levels increased with BMI in a dose response manner and the odds of having at least one positive specific IgE were elevated among obese children compared to normal weight children (OR: 1.35; 95% CI: 1.04-1.76). C-reactive protein levels were associated with both atopy and asthma, and may indicate a role for systemic inflammation for both outcomes. Breastfeeding was found to protect against obesity and asthma, but not atopy. The protective effect of breastfeeding against asthma was not modified by obesity or by atopy.;An increased risk of allergic disease and asthma may not be the most consequential health risk faced by overweight children. Nonetheless, it provides additional motivation for undertaking the difficult challenge to reduce childhood obesity.