Relationship between diabetes and risk of gastric cancer: A systematic review and meta-analysis of cohort studies

Patients with diabetes mellitus (DM) are at increased risk of developing several cancers; however, there is a lack of consensus on the relationship between gastric cancer (GC) and DM. This study aimed to explore the association between GC and DM based on the type and duration of DM. We searched nine databases from inception to December 1, 2021, and 40 cohort studies that evaluated the relationship between DM and the incidence of GC were included in this review. The summary relative ratios for the relationship of GC incidence with type 1 DM (T1DM) and type 2 DM (T2DM) were estimated using the fixed-effect and random-effect models, respectively. The risk of GC was 46% and 14% higher in individuals with T1DM and T2DM, respectively, than in those without diabetes. The risk of GC development in patients with diabetes showed a U-shape curve of change with DM duration. Our meta-analysis suggested that both T1DM and T2DM present a higher risk of GC development. The risk of GC may be influenced by the different time windows following the onset of diabetes. Future studies are required to explore the mechanism by which the duration of DM, antidiabetic medication use, and sex affect this association.