Several observational studies have examined vitamin D status in relation to asthma prevalence, severity, and clinical outcomes across different populations.
A cross-sectional, case-control study published in the Journal of Pediatrics (June 2010; 156(6)) evaluated 113 African American children between the ages of 6 and 20 years, comparing serum vitamin D levels in those with asthma and those without. Vitamin D deficiency was identified in 86% of children with asthma, compared with 19% of children in the control group.
Research published in the American Journal of Respiratory and Critical Care Medicine (January 14, 2010; e-published ahead of print) examined 54 nonsmoking adults with asthma and reported associations between lower vitamin D levels and greater airway hyperresponsiveness as well as impaired lung function. Participants with adequate vitamin D levels demonstrated better lung function and greater responsiveness to glucocorticoid therapy.
Additional pediatric data were reported in another study published in the Journal of Pediatrics (online September 25, 2010), which evaluated 75 Italian children with asthma. Only 9.4% of participants had vitamin D levels considered adequate. Lower vitamin D levels were associated with reduced breathing capacity, as measured by forced vital capacity (FVC) and the Childhood Asthma Control Test.
A larger observational study published in the Journal of Allergy and Clinical Immunology (July 2010; 126(1):52–58.e5) assessed vitamin D status in 1,024 children with mild to moderate asthma. Serum 25-hydroxyvitamin D levels below 30 ng/mL were observed in 35% of participants. Lower vitamin D status was associated with a higher risk of hospitalization or emergency department visits for asthma-related events.
Similar findings were reported in adults. A study published in Allergy, Asthma & Immunology Research (September 2013; 5(5):283–288) examined 121 adults with asthma in Costa Rica. Vitamin D insufficiency was defined as serum 25-hydroxyvitamin D levels below 30 ng/mL. When stratified by vitamin D status, severe asthma was present in 91% of participants with levels below 20 ng/mL and 74% of those with levels between 20 and 30 ng/mL, compared with 50% of those with sufficient vitamin D levels. Lower vitamin D status was also associated with a greater likelihood of hospitalization or emergency department visits in the preceding year.
Taken together, these studies describe consistent associations between lower vitamin D levels and asthma prevalence, severity, lung function measures, and healthcare utilization across pediatric and adult populations.
