Q. A 51-year-old Japanese woman comes to the emergency department due to severe chest pain. The patient states that the pain began half an hour ago. She has a history of similar episodes that have responded to sublingual nitroglycerin. The patient's past medical history is significant for diabetes, hypertension, dyslipidemia, and Reynaud's phenomenon. She has smoked 20 cigarettes per day for the last five years. Her vital signs are normal except for mild hypertension. A cardiopulmonary examination reveals no abnormalities. An electrocardiogram demonstrates ST segment elevation. Percutaneous coronary intervention is performed, which reveals no coronary obstruction. Regarding this patient's most likely diagnosis, which of the following is considered a risk factor?