NPPB and heart failure: In the final step, after forcing sex, age, and ABI into the model, the stepwise procedure was employed to select important confouders from among the following baseline characteristics: smoking status, BMI, systolic and diastolic blood pressure, serum levels of creatinine, IL-6, LDL, and NT-proBNP, presence of hypertension, diabetes, heart failure, history of stroke and myocardial infarction.