Evidence is accumulating rapidly for the association between vitamin D insufficiency, lung function, and corticosteroid use and sensitivity. Pivotal studies have been published examining a number of parameters, including effect of latitude, skin pigmentation, and body mass index.
In this month's JACI, Searing et al. provide the first report on prevalence of vitamin D insufficiency or deficiency in children with asthma living in latitudes higher than 20° N. [This article can be accessed for free at http://www.jacionline.org/article/S0091-6749(10)00505-1/fulltext.] Several significant correlations are reported: age, BMI, and positive skin tests are inversely correlated to vitamin D levels, while FEV1% and FEV1/FVC ratio are significantly correlated to vitamin D level.
The authors demonstrate significant association between inhaled corticosteroids, oral steroid use, and total steroid dose with low levels of vitamin D. They suggest that insufficient vitamin D might increase asthma severity, requiring greater treatment intervention or possibly that down-regulation of glucocorticoid pathways due to insufficient vitamin D dictates the need for increased steroid doses.
In vitro analyses of vitamin D activity in PBMCs demonstrated that vitamin D augments induction of MKP-1 and IL10 by steroids. Additionally, effects were observed that support vitamin D supplementation to increase steroid sensitivity, thereby permitting lower doses to obtain an optimal response.
We asked Dr. Daniel Searing, first author on the paper, about the implications of this research:
JACI: Is there baseline evidence of decreased vitamin D levels secondary to corticosteroid exposure in pediatric asthma patients?
Dr. Searing: Our study demonstrated correlations between vitamin D levels and steroid exposure in pediatric asthmatic patients from northern latitudes. To our knowledge, this is the first study looking at vitamin D levels in this patient population. Our study was not designed to examine causation of the low vitamin D levels. We are conducting a study currently looking to examine vitamin D levels in patients with asthma while also controlling for other known confounders (age, BMI, etc) to examine how strong the correlation of corticosteroid use and vitamin D levels is.
JACI: Is it possible that vitamin D insufficiency/deficiency is iatrogenic in children with asthma?
Dr. Searing: It is possible that low vitamin D levels are iatrogenic. However, the vitamin D levels in our patients with asthma seem to mirror levels in the general pediatric population. Whether escalating amounts of corticosteroid therapy in worsening asthma directly lower vitamin D levels versus other potential causes, such as vitamin D having effects on glucocorticoid pathways that leads to higher doses to achieve treatment effect is unknown at the present time. Future studies will help clarify this issue.
Do you have any questions for the authors, or comments about this study? We want to hear from you. Please feel free to post your own questions or comments. All questions and comments will be forwarded to the authors for a response.
Does it make sense to "supplement" with Vit D all children with asthma? In adults, I will use 30-50K per month-->what dose in children? Thank-you.
ReplyDeleteThe authors respond to the question from Dr. Wiens:
ReplyDelete"Thank you for your post and interest in our article. At this time, there is insufficient data to recommend supplementing with vitamin D all children with asthma, especially without knowing the child's vitamin D level. We would advocate, based on our findings, a low threshold for evaluating a child's vitamin D status with a 25-hydroxyvitamin D level. A prudent approach would be to consider checking vitamin D levels in children with asthma plus risk factors for a low level (for example elevated BMI, high northern latitude residence, poor dietary intake, elevated skin melanin concentration). Based on our data, children with asthma and on oral corticosteroids and/or high doses on inhaled corticosteroids should also be considered for vitamin D analysis. Since our data is retrospective and is a preliminary description of correlation, supplementation of children with asthma with vitamin D should continue to be done based on improving bone health, as there is no current data on supplementation having a benefit effect in asthma outcomes.
Therefore, we tend to supplement children with evidence of vitamin D deficiency and usually children with vitamin D insufficiency. Consultation with endocrinology is crucial for children with vitamin D deficiency rickets. Most experts agree children should be supplemented if their vitamin D levels are less than 20 ng/dL. We usually base supplementation in children on the recommendations of a recent review article on vitamin D deficiency in children (Pediatrics 2008;122;398-417)."