PPI Use Tracks With Higher IBD Event Rates After Prescription
A nationwide Danish cohort study has linked proton pump inhibitor exposure to higher rates of IBD-related hospitalization and IBD-related surgery, with the strongest association appearing in the first year after treatment began. The signal was large enough to raise immediate concern, yet the timing also points toward a familiar source of bias in observational medicine: patients may have received a PPI because gastrointestinal symptoms were already worsening, not because the drug itself triggered the flare.
The study followed 50,460 people with inflammatory bowel disease across Denmark from 2000 through 2022. Ulcerative colitis accounted for 67% of the cohort and Crohn’s disease for 33%. Five years after diagnosis, two-thirds of patients had been exposed to a PPI at some point, and 10% were in current treatment. In a population this large, PPI use is not an outlier; it is part of the background noise of chronic disease care, where dyspepsia, reflux, steroid-related prophylaxis, and overlapping abdominal complaints often lead to acid suppression.
The First-Year Signal Was Strongest for Hospitalization
For IBD-related hospitalizations, the weighted hazard ratio was 1.45 in the first year after PPI prescription, with a 95% confidence interval of 1.38 to 1.52. After that first year, the hazard ratio fell to 1.16, with a 95% confidence interval of 1.05 to 1.28. The pattern matters. A sharp early rise followed by attenuation fits the clinical reality of protopathic bias: the drug is often started in response to symptoms that are already on the path to hospitalization.
That timing is especially plausible in inflammatory bowel disease. Patients developing nausea, upper abdominal discomfort, poor oral intake, steroid exposure, or nonspecific abdominal symptoms may receive a PPI before the underlying inflammatory trajectory is fully recognized. Once a patient is close enough to hospitalization for a new prescription to enter the record, exposure and outcome can become tightly entangled in ways that mimic causation. In that setting, a PPI can look culpable simply because it enters the chart at the wrong moment.
Surgery Remained Elevated Beyond the First Year
The surgical endpoint told a more stubborn story. The weighted hazard ratio for IBD-related surgery was 1.21 during the first year after PPI prescription, with a 95% confidence interval of 1.11 to 1.32. After one year, the hazard ratio rose to 1.35, with a 95% confidence interval of 1.18 to 1.54. That later elevation is harder to dismiss as pure timing artifact, even if residual confounding remains a real possibility in a registry study of this kind.
A sustained surgical association raises several clinical possibilities. PPI use may still be acting as a marker for patients with more severe disease, higher healthcare utilization, or greater symptom burden. It may also reflect complex medication histories, including concurrent therapies that were not fully captured in the summary. The biological link is less obvious than for hospitalization, because PPIs are not established drivers of intestinal inflammation in the way that some other drugs can be. What the data do show is a persistent association that deserves caution rather than dismissal.
Why Protopathic Bias Fits the Early Pattern
Protopathic bias occurs when treatment is initiated for symptoms caused by disease that is already developing, making the medication appear to precede the outcome when it actually follows the earliest phase of illness. In inflammatory bowel disease, that problem can be especially difficult to untangle. Abdominal pain, nausea, reflux-like symptoms, and medication side effects can all overlap before a flare is formally recognized. If clinicians respond by starting a PPI, the prescription date becomes a misleading proxy for deterioration.
The study design tried to address this problem with historical propensity score weighting and by using current PPI use as the exposure. Investigators also allowed individuals to contribute more than one treatment episode, which expands the amount of information available but also reflects the messy reality of chronic care, where the same patient can move in and out of exposure over time. Even with those safeguards, observational data can never fully separate drug effect from disease momentum when treatment is prescribed in direct response to symptoms.
What the Cohort Says About Everyday IBD Care
The cohort size gives the findings real clinical weight. More than 50,000 patients is enough to detect patterns that smaller studies would miss, and the nationwide setting reduces the chance that the results are driven by one center or one referral pattern. At the same time, registry studies measure what is recorded, not every detail a clinician would want. Disease severity, symptom timing, over-the-counter medication use, and the exact reasons a PPI was prescribed may not be fully visible.
Even so, the practical message is straightforward. In patients with IBD, a new PPI prescription should not be read automatically as a cause of worsening disease. The first-year rise in hospitalization and surgery rates is more consistent with an already unstable clinical course than with a direct toxic effect from acid suppression. The later surgical signal keeps the question open, though, and it argues against complacency.
A Signal Worth Interpreting Carefully at the Bedside
For gastroenterologists and general clinicians, this study is a reminder that medication associations often reflect the clinical sequence in which drugs are started. PPIs are widely used, often for appropriate reasons, and the decision to prescribe them in a patient with IBD may simply identify someone already closer to a flare, admission, or operation.
The unresolved question is whether the persistent elevation in surgery reflects residual confounding, a true drug-related effect, or an interaction between symptom burden and disease severity that registry methods cannot fully resolve. Longer-term analyses with richer clinical detail, including symptom timing and endoscopic activity, will be needed before PPI exposure can be separated cleanly from the inflammatory course it so often accompanies.