High serum bilirubin is associated with lower prevalence of peripheral arterial disease among cardiac patients

Several studies have shown that subjects with higher serum bilirubin may have a lower risk of cardiovascular disorders. We herein investigated whether serum bilirubin concentration is associated with lower extremity ischemia among cardiology patients. In total, 935 patients without a history of angioplasty or bypass surgery of the lower limb arteries and who had bilateral ankle-brachial index measurements were included in the study. Peripheral arterial disease (PAD) was defined to be present when ABI of either or both sides was < 0.9. Overall, the serum total bilirubin concentration ranged between 0.1 and 2.7 mg/dL (normal range, 0.1-1.0 mg/dL). Across the bilirubin tertiles, age did not differ significantly. On the other hand, male patients (median 0.6 mg/dL, interquartile range (IQR) 0.4-0.7 mg/dL) had significantly higher bilirubin levels than female patients (median 0.5 mg/dL, IQR 0.4-0.7 mg/dL, P = 0.014). Logistic regression analysis showed that, as compared with the lowest bilirubin tertile (0.1-0.4 mg/dL), the highest tertile (0.7-2.7 mg/dL) was significantly negatively associated with prevalent PAD after adjusting for sex, age, eGFR, white blood cell count, inorganic phosphate, HbA1C, total and HDL cholesterol, triglycerides, current smoking, diabetic medication, and statin use. This association remained significant when only those with serum bilirubin in the normal range were included in the analysis. Among cardiology patients, serum bilirubin concentration was significantly negatively associated with prevalence of PAD. The underlying mechanism and therapeutic indications should be investigated in further investigations.