Nonlinear relationship between serum total bilirubin levels and initial ischemic stroke in patients with non-valvular atrial fibrillation

Abstract

Objective This study aimed to examine the relationship between total bilirubin levels and initial ischemic stroke in patients with non-valvular atrial fibrillation. Methods This was a retrospective study. Atrial fibrillation was diagnosed by 24-hour Holter electrocardiography and serum total bilirubin levels were divided into quintiles. Ischemic stroke was diagnosed by symptoms, signs, and a medical image examination. The multivariate Cox proportional hazards model and survival analysis were used to estimate the association of total bilirubin with initial ischemic stroke. Results We studied 316 patients with non-valvular atrial fibrillation. During follow-up, there were 42 (13.29%) first ischemic strokes. After multivariate adjustment, for each 1 µmol/L increase in total bilirubin, the risk of first ischemic stroke increased by 4% (95% confidence interval [CI]: 1.01, 1.07). When using the first quintile as the reference, from the second to fifth quintiles, the risks of first ischemic stroke were 0.52 (95% CI: 0.17, 1.65), 0.23 (95% CI: 0.06, 0.87), 0.92 (95% CI: 0.32, 2.67), and 1.33 (95% CI: 1.09, 4.41), respectively. The optimal cut-off point of total bilirubin for the lowest risk of ischemic stroke was 17.0 µmol/L. Conclusions Total bilirubin levels are nonlinearly associated with initial ischemic stroke in patients with non-valvular atrial fibrillation.