Serum 25-hydroxyvitamin D levels do not correlate with asthma severity in a case-controlled study of children and adolescents.

BACKGROUND There is no consensus on the association between vitamin D and asthma. OBJECTIVE To determine the relationship between 25-hydroxyvitamin D [25(OH)D] levels and asthma symptom severity in children and adolescents. METHODS A retrospective, case-control study of 263 subjects of ages 2-19 years with asthma who were compared to 284 non-asthmatic controls of similar ages. Subjects were excluded if they had diseases of calcium or vitamin D metabolism or were receiving calcium or vitamin D supplementation. Serum 25(OH)D was measured in all subjects. Asthma symptom severity, usually stratified into 6 steps, was stratified into five steps [1-5] based on the number and dose of controller medications used as outlined by the National Heart, Lung, and Blood Institute's guidelines. Mean 25(OH)D values were compared between the asthmatic patients and controls, as well as among the five steps of asthma symptom severity. Results were adjusted for age, sex, BMI, race and severity of asthma symptoms. RESULTS There was no difference in 25(OH)D between asthmatic patients and controls (28.64 +/- 10.09 vs. 28.42 +/- 11.47, p = 1.0). However, there was a significant difference in 25(OH)D between obese and non-obese asthmatic patients (23.33 +/- 7.67 vs. 30.16 +/- 10.20, p < 0.0001), as well as obese and non-obese controls (24.56 +/- 9.90 vs. 29.50 +/- 11.66, p = 0.003). Mean 25(OH)D levels did not vary significantly among the five steps of asthma symptom severity. CONCLUSIONS There were no differences in mean 25(OH) D levels between asthmatic patients and controls. Mean 25(OH)D level was significantly lower in both the obese asthmatic patients and obese controls. Asthma severity had no relationship to mean 25(OH)D levels.