Percent body fat, skinfold thickness or body mass index for defining obesity or overweight, as a risk factor for asthma in schoolchildren: which one to use in epidemiological studies?

Authors

  • Luis Garcia-Marcos,

    Corresponding author
    1. Pediatric Allergy and Pulmonology Units, Department of Pediatrics, Virgen Arrixaca University Children's Hospital, 30120 El Palmar, Murcia, Spain,
    2. Centre for Public Health Biomedical Network Research (CIBERSP), Pabellon Docente Universitario, Campus Ciencias de la Salud, 30120 El Palmar, Murcia, Spain,
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  • Jose Valverde-Molina,

    1. Department of Pediatrics, Los Arcos Hospital, Paseo de Colón 54, Santiago de la Ribera, 30720 San Javier, Murcia, Spain, and
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  • Maria L. Castaños Ortega,

    1. Department of Pediatrics, Los Arcos Hospital, Paseo de Colón 54, Santiago de la Ribera, 30720 San Javier, Murcia, Spain, and
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  • Manuel Sanchez-Solis,

    1. Pediatric Allergy and Pulmonology Units, Department of Pediatrics, Virgen Arrixaca University Children's Hospital, 30120 El Palmar, Murcia, Spain,
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  • Antonia E. Martinez-Torres,

    1. Pediatric Allergy and Pulmonology Units, Department of Pediatrics, Virgen Arrixaca University Children's Hospital, 30120 El Palmar, Murcia, Spain,
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  • Jose A. Castro-Rodríguez

    1. School of Medicine, Pontificia Universidad Catolica de Chile, Lira 44 1er piso, Santiago, Chile
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Luis Garcia-Marcos, Pediatric Pulmonology Unit, Department of Pediatrics, Virgen Arrixaca University Children's Hospital, 30120 El Palmar, Murcia, Spain. E-mail: lgmarcos@um.es

Abstract

None of the epidemiological studies indicating that obesity is a risk factor for asthma in schoolchildren have used the percent body fat (PBF) to define obesity. The present study compares the definition of obesity using body mass index (BMI), PBF and the raw sum of the thickness of four skinfolds (SFT) to evaluate this condition as a risk factor for asthma. All classes of children of the target ages of 6–8 years of all schools in four municipalities of Murcia (Spain) were surveyed. Participation rate was 70.2% and the number of children included in the study was 931. Height, weight and SFT (biceps, triceps, subscapular and suprailiac) were measured according to standard procedures. Current active asthma was defined from several questions of the International Study of Asthma and Allergies in Childhood questionnaire. Obesity was defined using two standard cut-off points for BMI and PBF, and the 85th percentile for BMI, PBF and SFT. The highest quartile of each type of measurement was also compared with the lowest. A multiple logistic regression analysis was made for the various obesity definitions, adjusting for age, asthma in the mother and father and gender. The adjusted odds ratios of having asthma among obese children were different for boys and girls and varied across the different obesity definitions. For the standard cut-off points of BMI they were 1.19 [95% confidence interval (CI) 0.41–3.43] for girls and 2.00 (95% CI 0.97–4.10) for boys; however, for PBF (boys 25%, girls 30%) the corresponding figures were 1.54 (95% CI 0.63–3.73) and 1.20 (95% CI 0.66–2.21). BMI, PBF and SFT showed more consistency between each other when using the other cut-off points. BMI, PBF (except standard cut-off points) and SFT produce relatively comparable results when analysing the interaction between obesity and asthma.

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