In a paper online Sept. 8 in The American Journal of Gastroenterology, Bjørn Kantsø of Statens Serum Institut in Copenhagen and colleagues note that the inappropriate immune response against infective agents seen in IBD patients may increase the risk of bacterial infections. This might also be true of treatment with immunomodulators.
To investigate further, the team conducted a population-based cohort study spanning 1977 to 2012, and involving more than 74,000 IBD patients and close to 1.5 million IBD-free controls.
During more than 824,000 person-years of follow-up, 277 IBD patients were diagnosed with IPD (0.37%) as were 3,984 controls (0.27%).
Patients with Crohn’s disease (CD) had a 2-fold higher risk of IPD than controls (hazard ratio, 1.99) and ulcerative colitis patients had a 1.5-fold higher risk (HR, 1.46).
The risk overall was particularly high in the first year after IBD diagnosis (HR, 2.97). This declined to 1.78 at two to four years after diagnosis. In UC patients, the corresponding hazard ratios were 2.15 and 1.35.
UC patients who had used azathioprine had a significantly higher risk of IPD than those not receiving azathioprine (HR, 2.38). This was not the case for CD patients or of use of a number of other drugs including corticosteroids, however.
The researchers note that few studies have examined the impact of vaccination in IBD patients. Kantsø told Reuters Health by email, “The finding in this study highlights the numerous recommendations on routine pneumococcal vaccination; however, it is uncertain whether these recommendations are followed.”
“The study methods seem rigorous,” commented Dr. Edward V. Loftus, director of the Inflammatory Bowel Disease Interest Group at the Mayo Clinic in Rochester, Minn.
“We know from the old biomedical literature that a small percentage of ulcerative colitis patients can develop ‘functional asplenism’, and these patients are at risk for infections with encapsulated organisms such as Streptococcus pneumonia,” he told Reuters Health by email. “However, this would explain only a small proportion of these infection cases.”
He added, “The finding of an increased risk of pneumococcal disease both before and after the diagnosis suggest that perhaps the same alterations in the immune system which might predispose the development of inflammatory bowel disease also increase the risk of certain infections.”