~18 % of stomach cancer cases
||Human Homo sapiens
||Patel TN, Roy S, Ravi R. Gastric cancer and related epigenetic alterations. Ecancermedicalscience. 2017 Jan 17 11: 714. doi: 10.3332/ecancer.2017.714. p.2 bottom paragraphPubMed ID28144288
||P.2 bottom paragraph: "Following an erratic lifestyle for a prolonged period of life is an important causative factor of gastric cancer. Studies have revealed that approximately 18% of stomach cancer cases can be traced to tobacco smoking."