Date of Award

2010-01-01

Degree Name

Master of Science

Department

Public Health

Advisor(s)

Mary-Margaret Weigel

Second Advisor

Rodrigo X. Armijos

Abstract

Background and Significance. Atopy is a hypersensitivity disorder that mainly affects the mucous membranes and the skin. It is reported to be the most prevalent type of clinical allergy syndrome. Persons who have atopy suffer from various combinations of asthma, rhino-conjunctivitis and/or eczema. Atopy is defined as an inherited predisposition to generate IgE against common environmental allergens. Atopy is a type I hypersensitivity condition mediated by IgE immune response, while allergy is any excessive immune response to a foreign antigen. Thus, all atopic disorders are allergic response but some allergic conditions are not atopic per se.

The etiology of pediatric allergic diseases is complex; it involves multiple phenotypes that are influenced by a variety of genetic, host, and environmental factors. The scientific literature also suggests that certain environmental factors may act to either promote or protect against the development of allergic diseases, depending upon when exposure occurs such as in the prenatal period, early infancy, or later childhood. While some of these such as exposure to tobacco smoke and other indoor and outdoor ambient air pollutants are well documented, the evidence for others is less certain. It is important to investigate these other environmental influences in order to better understand the potential for allergic disease and ways to reduce risk in children. There are no published data the prevalence of childhood atopy in the U.S.-Mexico border region.

Objectives. The major objectives of the current study were to investigate the prevalence and environmental factors associated with the development of childhood atopy in young Mexican schoolchildren. These included familial allergy history, size at birth, respiratory infection history, overweight/obesity, breastfeeding, early weaning, type of weaning foods, and parasitic infections).

Hypothesis. It was hypothesized that the combination of a positive familial allergy history, a proxy for genetic background, in concert with early exposure to certain environmental allergens alters Th1-Th2 immune profile and increases the risk for developing atopy during childhood. It also was hypothesized that overweight/obesity causes chronic inflammation (generated in adipocytes) thereby increasing the risk for childhood atopy by elevating cytokine tumor necrosis factor -α (TNS -alpha) from adipose tissue, from interleukins 1 and 6 and leptin.

Methods. The survey was carried out in a public elementary school in Ciudad Juarez, Mexico. A total of 175 children attending the school who were enrolled in grades 1-4 completed the study. Only one child per family was allowed to participate to prevent oversampling by household. Data were collected from the student participants using a structured questionnaire containing closed and open-ended questions on child and household characteristics (sociodemographic, housing and living conditions, and child health history). Participants also underwent a comprehensive physical examination and anthropometric assessment. Serial fecal samples (3) were collected and analyzed for protozoal and helminth infections. The descriptive data were analyzed as number and percent or as means + S.D. Two by two contingency table analysis with corrected X2 or Fisher's exact test, were used as appropriate to assess the bivariate categorical data. Students' independent t-test or one-way ANOVA was used to analyze continuous data, as appropriate. Multiple logistic regression analysis was employed to further analyze variables identified as significant (> 0.05) in the bivariate analyses.

Results. Slightly more than one-fifth (17.1%; 30) of the 175 child participants had one or more atopic conditions. Six children (2.9%) had asthma and 14.3% (25) had other conditions such as rhinoconjunctivitis (hay fever) and atopic dermatitis. Five of the six children (80%) with asthma also had other atopies. The children were reported to have several different types of allergy triggers. These included dust/soil, pollen, mold, furred animal dander, foods (i.e., avocado, pizza, tunafish, peach, egg, and fried meat), drug (penicillin, sulfa drugs), and stuffed animal toys. Children with a familial history of atopy (34.8%; 16) were more likely than those without (10.9%; 14) to develop asthma or other atopic conditions during childhood (OR= 4.38, 95% C.I. = 1.93, 9.97; P < 0.0001). Children who were fed with any artificial formula during the first 3-4 months (13.2%; 7) were not at increased risk than others (18.9%; 23) to develop atopy (OR=1.53; 0.62, 3.81. Children who were exclusively fed with breast milk for the first six months after birth (3.2%; 1) had a marginally reduced risk than others (20.1%; 29) for developing atopy (OR= 0.13; 95% CI= 0.17, 1.01). It was not possible to assess the contribution of intestinal helminth infection to childhood atopy due to the absence of these in any serial stool samples.

The environmental factors identified as significant in the bivariate analyses included current obesity, early solid food introduction (< 4 mos. of age), meat/fish introduction (< 12 mos. of age) and a positive history for severe respiratory infection history. The results of the multiple regression analysis revealed that childhood obesity (AOR=2.78; 95% C.I.= 1.11, 6.96), early solid food introduction (AOR=3.66; 95% C.I.= 1.43, 9.33), and meat/fish introduction before the first year of life (AOR=3.15; 95% C.I.= 1.24, 8.02) remained significant even when controlling for the influence of the other variables in the model. However, the contribution of severe respiratory infection history was no longer apparent and was dropped from the model (AOR=3.36; 95% C.I.= 0.95, 12.0).

Conclusions and Recommendations. The study results confirmed that young children with history of family allergy are at very high risk for developing atopy compared to others. The three environmental factors (i.e., premature introduction of solid food and foreign animal proteins, and child obesity) associated with an increased risk for atopy are all potentially modifiable through dietary and physical activity education/promotion.

Language

en

Provenance

Received from ProQuest

File Size

62 pages

File Format

application/pdf

Rights Holder

Julia Laura Alvarez

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