Electronic Nicotine Delivery Systems and Clinical Outcomes in Adults With Inflammatory Bowel Disease: A Systematic Review of Emerging Evidence.

Electronic nicotine delivery systems (ENDSs), including e-cigarettes and vaping, are increasingly used by adults with inflammatory bowel disease, often during smoking cessation or transition from combustible cigarettes, yet their clinical implications remain uncertain. We conducted a systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 statement. MEDLINE, Embase, Web of Science, and Scopus were searched from inception through December 18, 2025, together with grey literature sources; the search was rerun on April 24, 2026, identifying no additional eligible studies. Two reviewers independently screened studies and extracted data, and risk of bias was assessed using design-appropriate tools. Four observational studies involving 1,869 participants, of whom 178 were ENDS users, met inclusion criteria. In nonoperative settings, a matched case-control study found no association between current e-cigarette use and a composite outcome of biologic initiation or change, hospitalization, or surgery; smaller cohorts were imprecise. In postoperative Crohn's disease, endoscopic recurrence at one year was higher among exclusive e-cigarette users than among nonsmokers, with a directionally elevated but statistically nonsignificant adjusted estimate and higher biochemical activity also observed. Available evidence does not demonstrate a consistent association between current ENDS use and major inflammatory bowel disease outcomes in nonoperative settings, but a possible signal exists for higher postoperative endoscopic recurrence among e-cigarette users. Larger prospective studies with standardized exposure definitions are needed.