Shared and additional risk factors for decrease of toe-brachial index compared to ankle-brachial index in Japanese patients with diabetes mellitus.

OBJECTIVE: Some diabetic patients have a low toe-brachial index (TBI) despite their normal ankle-brachial index (ABI). We statistically investigated whether the impact of risk factors on TBI would be different compared to ABI.

RESEARCH DESIGN AND METHODS: We used a database of 1738 limbs of consecutive 869 Japanese diabetic patients whose ABI and TBI were simultaneously evaluated. We developed a common regression model to ABI and TBI by extending the linear mixed model, and statistically detected the difference in the impact of risk factors between the two indices.

RESULTS: Sex, smoking, proteinuria, hypertension, and history of stroke and coronary artery disease were common independent risk factors for the decrease of ABI and TBI; their impacts on ABI and TBI were not significantly different. On the other hand, the impact of age, diabetic duration, and body mass index was significantly different between the two indices (all p < 0.05). Age and body mass index were significantly associated with TBI but not with ABI. Diabetic duration had a significant impact both on TBI and ABI, but the impact on TBI was significantly greater than that on ABI (β = -0.144 vs. -0.087; p < 0.05). In the population with normal ABI, patients with these risk factors had a higher prevalence of decreased TBI.

CONCLUSIONS: The risk factors for the decrease of ABI and TBI were not identical in Japanese diabetic patients. Age, diabetic duration and body mass index were associated with reduced TBI in patients with normal ABI.