PURPOSE OF THE STUDY.
Epidemiologic studies suggest a link between vitamin D deficiency in early life and the development of asthma later in life. The purpose of this study was to measure serum vitamin D levels in children with asthma and compare these children with healthy, nonasthmatic controls.
Asthmatic (n = 483) and healthy control (n = 483) children were recruited from the Pediatric Allergy-Immunology Clinics of Hamad General Hospital and the Primary Health Care Clinics in Qatar from October 2009 to July 2010. All children were aged <16 years, and asthma was diagnosed by a physician.
Parents of all children completed extensive questionnaires documenting demographic characteristics, child’s feeding practice, and vitamin D intake. Serum 25-hydroxyvitamin D, calcium, phosphorus, alkaline phosphatase, magnesium, creatinine, and parathyroid hormone assays were performed. Overall, subjects with vitamin D levels <20 ng/mL were deemed deficient, levels of 10 to 19 ng/mL moderately deficient, and levels <10 ng/mL were considered severely deficient.
Overall, 68.1% of the children with asthma and 36.1% of the control children were vitamin D deficient. Asthmatic children had significantly higher degrees of moderate (41.8% vs 25.1%) and severe (26.3% vs 11.0%) vitamin D deficiency compared with healthy controls (P < .001). Positive familial history of vitamin D deficiency (35.6%; P = .005) and asthma (36.4%; P = .009) were significantly higher in children who had asthma. Along with vitamin D deficiency, asthmatic children also had reduced phosphorus (P < .001) and magnesium (P = .001) levels but elevated serum alkaline phosphatase (P < .001) and immunoglobulin E (P < 0.001) levels. The majority of children who had asthma had less exposure to sunlight (66.7%; P = .006) and less physical activity (71.3%; P < .001). Vitamin D deficiency was the strongest predictor of asthma in this population (odds ratio: 4.82 [95% confidence interval: 2.41–8.63]; P < .001).
The current study revealed that the majority of children who had asthma had a vitamin D deficiency compared with control children. Vitamin D deficiency was the major predictor of asthma in Qatari children.
Vitamin D deficiency has been linked to an increased incidence of asthma and increased severity of asthma in children. This study provides additional epidemiological support for the association between vitamin D deficiency and asthma. Further studies examining the potential mechanisms of vitamin D in asthma pathophysiology and intervention studies aimed at improving vitamin D status in children who have asthma are needed to elucidate the nature of this association.
- Copyright © 2012 by the American Academy of Pediatrics