MSFinals-1468

A 67-year-old man presents with nausea, vomiting, epigastric discomfort and weight loss over the last 2 months. On questioning, he describes postprandial fullness and loss of appetite. He denies any dysphagia, melaena or haematemesis. He has a long-standing history of heartburn. He has no other relevant past medical history. Investigations reveal iron deficiency anaemia. Endoscopy confirms gastric cancer.
What is a risk factor for gastric cancer in this 67-year-old man?