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INTRODUCTION
Several studies have evaluated the association between obesity and asthma [12345], atopic dermatitis [6789] and allergic sensitization to foods [10], but obesity was negatively associated with the prevalence of allergic rhinitis or there was no relationship [111]. Gender is also likely to be important when examining the relationship between allergic disease and obesity in children and adults [3], but the evidence is inconclusive. The relationship between obesity and asthma [12] and atopic dermatitis [1] is also inconclusive. The objective of the present study, a part of the epidemiology of allergic disorders in Chinese study, was to analyze the association between the different body mass index (BMI) categories (normal weight, overweight, and obesity) and allergic diseases in a population of Chinese children aged 2–14 years.
MATERIALS AND METHODS
Study population
The epidemiology of allergic disorders in China study used the methodology of the National Study of asthma and Allergies in Childhood [13]. The study participants were selected by cluster-type stratified random sampling.
The first part of the project (a questionnaire survey) was carried out on a group of 4,132 participants with the response rate of 80.5% and eventually 3,327 completed questionnaires were accepted. It involved three age groups of children, 2–6 years old and 7–12 years old, and 13–14 years old. There were 787 (23.7%) 2–6 years old, 2,190 (65.8%) 7–12 years old, and 350 (10.5%) 13–14 years old. Of the respondents, 1,663 (50%) were female and 1,664 (50%) were male. In the medical evaluation part of the study, they were all assessed on an out-patient basis. The study group design is shown in Table 1.
Questionnaire-based survey
The questionnaire was based on the literature that has been published [13]. The diagnosis of allergic diseases was carried out by experienced doctors.
Medical evaluation
Asthma was diagnosed according to the criteria [13] based on Global Initiative for Asthma, allergic rhinitis using the Allergic Rhinitis and its Impact on Asthma criteria and atopic dermatitis using the Hanifin and Rajka criteria.
Anthropometric measurements
In those participating, we measured weight without shoes or outer clothing (to nearest 0.1 kg) and height (to nearest 0.1 cm). BMI was calculated as weight/height2 (kg/m2). BMI was analyzed as a categorical variable divided into three categories (normal weight, overweight, and obesity). According to the accepted definition in epidemiological studies, Children's BMI referred to the new Chinese growth charts and obesity was diagnosed when BMI was >95th percentile, overweight when BMI was >85th and <95th percentile and normal weight when BMI was >3rd and <85th percentile [14].
Statistical evaluation
A chi-square test or Fisher exact test (for small sample sizes) was used in the statistical analysis. To determine the strength of association and the dependence between variables, chisquare statistics and odds ratios were calculated. Results were considered to be statistically significant at p < 0.05.
RESULTS
The prevalence of obesity and overweight and of allergic disease in the study population is shown in Table 2. Obesity children had no increase of asthma, food allergy, and drug allergy. We found no effect of being overweight on allergy, diseases. Detailed data are shown in Table 3.
There was a significantly higher prevalence of allergic rhinitis in obese (odds ratio [OR], 1.48; p < 0.05) girls. Detailed data are shown in Table 4.
DISCUSSION
To our knowledge, the present study is first one in this part of middle southern-China assessing the relationship between overweight and obesity and the prevalence of allergic diseases among children.
In the literature, there are conflicting reports about the influence of BMI on allergic status. Although the association between obesity and asthma has been gaining more attention, few studies have been conducted concerning the relationship between obesity and other allergic diseases. The results are ambiguous and often contradictory. Most of the published studies suggest that being overweight and obese has a positive association with atopic dermatitis in children and adults. However, there are also reports of the nonexistence of such a relationship. We found obesity was significantly associated with an increased prevalence of allergic rhinitis and atopic dermatitis. In conclusion, our cross-sectional study showed that being obese is associated with an increased prevalence of allergic rhinitis and atopic dermatitis. Higher BMI was no relationship with the occurrence of asthma, food allergy, and drug allergy, in this research.
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