Smoking and alcohol, both alone and in combination, for risk of gastric cancer: A systematic review

Introduction: Stomach cancer is the fifth most common cancer and the fourth leading cause of cancer deaths worldwide in 2020. Moderately increased risk of stomach cancer has been associated with tobacco smoking and Alcohol drinking. In this systematic review, we summarized the current knowledge on the relation between smoking and alcohol, both alone and in combination, to the risk of gastric cancer. Method: This study was conducted in 2023 with a structured overview in the Science Direct, PubMed, and Web of Science (ISI) databases. We investigated the studies that were published between 2010 and 2023. In the first step, articles were extracted based on their titles and abstracts; the quality of 58 articles was evaluated using the STORBE tool. Inclusion criteria were the English language (first step), the year of the study, and the study type (second step). Results: Of these 39 articles, 17 ones were case-control studies, 21 were cohort studies, one was a descriptive study. eleven articles were related to alcohol consumption and risk of gastric cancer, twenty-three articles were related to smoking and risk of gastric cancer, and five articles were related to smoking and alcohol consumption in combination and risk of gastric cancer. Many studies reported a significant association between alcohol and gastric cancer risk. Also, three studies showed that smoking acts as a risk factor for developing gastric cancer only in certain genotypes and not in all people. Conclusion: Based on the best of our knowledge and present studies, consumption of alcohol and smoking are risk factors of gastric cancer. It is better to conduct more studies on this issue in different populations in the future. We also suggest that future studies focus more on the intracellular mechanisms of these associations than on epidemiological outcomes