Review Question - QID 107120

A 65-year-old man is brought to your office by his wife. He has not seen a doctor in decades. The patient has a longstanding history of “heartburn” following meals, for which he takes over-the-counter antacids. He is now having difficulty swallowing food. He has lost 15 pounds in the last three months. On further review, he has a 5 pack-year smoking history. He enjoys a beer with dinner several nights a week. An upper endoscopy is performed, with the finding shown in Figure A found just proximal to the gastroesophageal junction. Which of the following was the most important predisposing risk factor for his disease?