INS and diabetes mellitus: Pre-diabetic and untreated diabetes were not associated with increased risk for atrial fibrillation. Type 2 diabetics had an increased risk of atrial fibrillation [1.35 (1.14–1.60)]. No association was observed between fasting glucose or insulin and atrial fibrillation but there was a positive association between HbA1c levels and atrial fibrillation in both diabetic and non-diabetic subjects.