Published Dec. 31, 2016
Journal of Allergy and Clinical Immunology

In examining the distinction between correlation and causation, researchers found that, despite multiple studies demonstrating correlation, vitamin D deficiency does not cause pediatric asthma, nor asthma exacerbations.

Vitamin D deficiency is highly prevalent in asthma, the most common chronic childhood disease. Researchers had long hypothesized that it had a causative effect through regulation of airway reactivity, sensitivity to corticosteroids, or modulation of immune function.

It took a Mendelian randomization approach, and a team of researchers that included Erik Hysinger, MD, MS, to demonstrate that Vitamin D deficiency is not in the causal pathway. Instead, asthma predisposes children to low levels of vitamin D.

Hysinger joined our Division of Pulmonary Medicine following his fellowship at Children’s Hospital of Philadelphia, where he was a co-first author on the study. It was published Dec. 31, 2016, in the Journal of Allergy and Clinical Immunology.

“The primary finding that low 25(OH)D is not in the causal pathway of asthma or asthma exacerbations was entirely unclear to us prior to performing the study,” Hysinger says.

The study cohort included 12,842 children with asthma. Previous epidemiology studies revealed that vitamin D is inversely correlated with the risk of asthma, but supplementation with vitamin D did not improve asthma health.

“In fact,” Hysinger says, “these differing data, along with confusion in the field, were the primary reasons that we wanted to do the study.”

In recent years, researchers have increasingly used Mendelian randomization to examine causality when association studies show one factor that is largely determined by genetics could impact disease.

“It was very exciting to use a novel technique to further investigate and provide new insight into this relationship,” says Hysinger.