Association of borderline ankle-brachial index with mortality and the incidence of peripheral artery disease in diabetic patients

Objective: Peripheral artery disease (PAD) and diabetes mellitus are significant risk factors for all-cause death or cardiovascular death. PAD occurs more frequently in diabetic than in non-diabetic patients. However, the association of ankle-brachial index (ABI), especially borderline ABI, with clinical outcomes has not been fully elucidated in diabetic patients. This study aimed to investigate the association of ABI with mortality and the incidence of PAD in Japanese diabetic patients. Methods: This observational study included 3981 diabetic patients (61.0±11.8 years of age, 59.4% men), registered in the Kyushu Prevention Study for Atherosclerosis. Patients were divided into 3 groups according to the value of ABI at baseline: ABI ≤0.90 (abnormal ABI:354 patients), 0.91≤ABI≤0.99 (borderline ABI:333 patients), and 1.00≤ABI≤1.40 (normal ABI:3294 patients). Results: Cumulative incidence of all-cause death was significantly higher in patients with abnormal and borderline ABI than in those with normal ABI (34.4% vs. 13.5%, P<0.0001 and 26.1% vs. 13.5%, P<0.0001, respectively). In multivariate analysis, the risks for all-cause death in patients with abnormal ABI (HR:2.16; 95%CI:1.46-3.14; P=0.0002) and borderline ABI (HR:1.78; 95%CI:1.14-2.70; P=0.01) were significantly higher than in those with normal ABI. The incidence of PAD was remarkably higher in patients with borderline ABI than in those with normal ABI (32.2% vs.9.6%, P<0.0001). After adjustment, the risk for PAD was significantly higher in patients with borderline ABI than in those with normal ABI (HR:3.10; 95%CI:1.90-4.95; P<0.0001). Conclusions: Borderline ABI in diabetic patients was associated with significantly higher risks for mortality and PAD compared with normal ABI.