Date of Award

2013-01-01

Degree Name

Doctor of Philosophy

Department

Interdisciplinary Health Sciences

Advisor(s)

Joseph Tomaka

Abstract

About 23 million people, including almost 10 million children, have asthma in the United States. Asthma prevalence is higher among families with lower incomes living at the US/ Mexico Border and represents the most common serious chronic diseases of childhood. It is the third-ranking cause of hospitalization among children under 15, (De Frances, 2007) as well as the cause of seven million physician visits and nearly 200,000 hospitalizations every year. An average of one out of every ten school-aged children has asthma and, 13 million school days are missed each year due to asthma symptoms (Akinbami, 2006). According to the National Heart, Lung, and Blood Institute (NHBLI, 2009) annual expenditures for health and lost productivity due to asthma are estimated at over $20 billion. Recently, research has shown that low serum levels of Vitamin D might be associated with poor asthma control (Bhrem, 2010), but the exact mechanism is still unknown. Studies about the potential effect of vitamin D are largely based on observational studies that lack measurements of serum levels.

This Dissertation used National Health and Nutrition Examination and Survey (NHANES) data from 2005-2006 to examine the relationship between vitamin D, asthma and allergy among 1884 U.S. children age 6-15. Data from 2005-2006, included serum levels of vitamin D [25(OH) D], questionnaires of asthma and allergy symptoms, sociodemographic characteristics, and assays for total and allergen-specific IgE. A mediation analysis was performed to explore the mediation effect of IgE between the relationship of vitamin D and asthma symptoms.

The prevalence of asthma observed in this cross-sectional study was 16.3% .The majority of study children (86%) had serum vitamin D levels below an accepted optimal threshold < or =30 ng/mL, with mean ± SDs of 22.13 ± 7.8 ng/mL.

The risk of asthma diagnosis was higher among children with deficient serum levels of 25(OH) D compared with children with sufficient vitamin D status (OR, 1.53; 95% CI, 1.00-2.33). Similarly, allergy diagnosis was associated with vitamin D deficiency (OR, 1.58; 95% CI (1.10-2.27) in a multivariate model adjusted for age, gender, parental education and BMI.

The mediation analysis showed that vitamin D was negatively related to asthma severity and that Immunoglobulin E [IE= -.013, 95% CI [-.023,-005] mediated this relationship. Gender moderated this relationship such that these associations were stronger for boys than for girls. Overall, the results suggest that addressing reduction of vitamin D deficiencies could be a potential public health strategy to decrease asthma and allergy severity in children

Language

en

Provenance

Received from ProQuest

File Size

94 pages

File Format

application/pdf

Rights Holder

Silvia Flores

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