Role of diabetes and insulin use in the risk of stroke and acute myocardial infarction in patients with atrial fibrillation: A Medicare analysis.

Background: Atrial fibrillation (AF) is associated with elevated risk for ischemic stroke and myocardial infarction (MI). The aim of the study is to assess the role of insulin use on the risk of stroke and MI in AF patients with diabetes.

Methods: We identified Medicare beneficiaries with new AF in 2011 to 2013. Primary outcomes were ischemic stroke and MI. Multivariate Cox regression models were used to assess the association between AF and time to stroke and MI. We adjusted for anticoagulant as a time-dependent covariate.

Results: Out of 798,592 AF patients, 53,212 (6.7%) were insulin-requiring diabetics (IRD), 250,214 (31.3%) were non-insulin requiring diabetics (NIRD) and 495,166 (62%) were non-diabetics (ND). IRD had a higher risk of stroke when compared to NIRD (adjusted HR: 1.15, 95% CI 1.10-1.21) and ND (aHR 1.24, 95% CI 1.18-1.31) (P < .01 for both). The risk of stroke was higher in NIRD compared to ND (aHR 1.08, 95% CI 1.05-1.12). For the outcome of MI, IRD had a higher risk compared to NIRD (aHR 1.24, 95% CI 1.18-1.31) and ND (aHR 1.46, 95% CI 1.38-1.54)]. NIRD had a higher risk compared to ND (aHR 1.17, 95% CI 1.13-1.22). Anticoagulation were most effective at preventing stroke in ND [0.72 (0.69-0.75)], and NIRD [0.88 (0.85-0.92)], but were not associated with significant reduction in stroke in IRD [0.96 (0.89-1.04)].

Conclusion: There is an incremental risk of ischemic stroke and MI from non-diabetics to non-insulin diabetics with the highest risk in insulin users. Protective effect of anticoagulation is attenuated with insulin use.