Inhaled and oral corticosteroids are often used to treat acute and chronic asthma. The negative effects of corticosteroids on bone mineral density are well established, particularly when given orally or intravenously. Vitamin D insufficiency, a condition present in about 55% of the US population, has also been associated with decreased bone density. However, the combined effect of vitamin D insufficiency and exposure to corticosteroids on bone health in people with asthma has not been well studied.
In their article in The Journal of Allergy & Clinical Immunology (JACI), Tse et al examined whether children with asthma who have lower vitamin D levels were more susceptible to the adverse effects of corticosteroids on bone mineral accretion, which represents the average gain of bone mineral density over time. A total of 780 children were followed over a period of approximately four years as part of the Children Asthma Management Program (CAMP) trial and had their bone mineral density measured at the beginning and the end of the trial.
The researchers found that vitamin D insufficiency at the beginning of the trial exacerbated the negative effect of oral corticosteroids on bone mineral accretion over the four years in boys. This effect was most notable in boys taking the equivalent of two or more courses of oral corticosteroids per year. The combined effects of vitamin D insufficiency and exposure to oral corticosteroids were not seen in girls, possibly due to their overall more advance pubertal and bone maturational stages, which can lead to decreased susceptibility to the negative effects of vitamin D insufficiency and corticosteroids on bone density.
These findings by Tse et al may have important clinical implications given the high prevalence of vitamin D insufficiency and the common usage of oral corticosteroids in children with asthma. Further research is needed to explore whether vitamin D supplementation can confer clinical benefits on bone health in this situation, especially in boys with poor asthma control.