WASHINGTON — Individuals with low levels of vitamin D were not more likely to develop Crohn’s disease, but Crohn’s patients were more likely to have low vitamin D levels in a recent study, a presenter said.
Investigators concluded that these findings clarify the challenge of “reverse causation” regarding vitamin D deficiency in Crohn’s disease, suggesting that low vitamin D levels are the result of Crohn’s disease rather than a significant contributing cause.
“What we found is that before diagnosis, vitamin D levels were not associated with Crohn’s disease. However, after diagnosis, Crohn’s disease was associated with low vitamin D levels,” Berkeley Limketkai, MD, of Stanford University School of Medicine, said during his presentation. “So, these data suggest that perhaps previous associations of low vitamin D levels leading to worse Crohn’s disease may actually have been instead influenced by reverse causation.”
In a prospective nested case-control study using U.S. military personnel data spanning 1998-2011 Limketkai and colleagues measured vitamin D levels before and after diagnosis in 240 patients with Crohn’s disease and the same number of matched controls without Crohn’s. They obtained serum samples from the Department of Defense Serum Repository taken at three different points in time: 3-8 years before diagnosis (or time of index for controls); 3 months to 3 years before diagnosis; and after diagnosis.
The investigators found no association between Crohn’s disease incidence and pre-diagnosis 25-hydroxyvitamin D levels. In contrast, they found an inverse association between Crohn’s disease and vitamin D levels after diagnosis (OR = 0.74; 95% CI, 0.59–0.94; P = 0.01). The investigators noted they observed no interactions between polymorphisms in vitamin D-related genes and vitamin D levels.
Limketkai noted that the study was limited by its primarily male U.S. military cohort, lack of more granular data, discrete measurements of time points and small sample size. – by Adam Leitenberger
Limketkai B, et al. Abstract 54. Presented at: Digestive Disease Week; June 2-5, 2018; Washington, D.C.
Disclosures: Limketkai reports no relevant financial disclosures. Please see the DDW faculty disclosure index for a list of all other authors’ relevant financial disclosures.