Background and aims: Apparent aspiration is a notable adverse event during gastrointestinal endoscopy under sedation (GIES), but data about inapparent aspiration are scarce. Generally, particularly older patients are at higher risk of suffering from adverse events. Objective: The objective of this article is to determine the risk of pneumonia, lower respiratory tract infection (LRI) and systemic inflammatory activation after GIES, especially in patients of at least 65 years. Methods: The retrospective case-control study included 250 patients undergoing GIES and assigned age-, gender-and time of performance-matched controls without invasive procedure or sedation (ratio 1:1). Results: On day 3 patients of advanced age presented with both pneumonia and LRI more often (2.6 vs. 0.0%, p ¼ 0.041 and 7.8 vs. 2.5%, p ¼ 0.034, respectively). In general, several inflammatory parameters increased significantly after GIES (i.e. white blood cell count (increase of ! 25%) 18.6 vs. 6.9%, p < 0.001), leading to more frequent antibiotic treatment (6.8 vs. 1.6%, p ¼ 0.004). The effects were less pronounced on day 7. Conclusions: Patients of advanced age carry an increased risk of pneumonia and LRI after GIES. Patients are generally more likely to feature inflammation and to receive antibiotic treatment.