A high normal ankle-brachial index is associated with proteinuria in a screened cohort of Japanese

OBJECTIVES: We hypothesized that ankle-brachial index (ABI) increased with age as a result of arterial stiffness, and decreased when flow-limiting atherosclerotic stenosis occurred in the lower limbs. As arterial stiffness is associated with proteinuria, we investigated the relationship between ABI and prevalence of proteinuria. METHODS: A cross-sectional study of ABI and proteinuria with 13,193 participants aged 21-89 years (53% women) from health checkups between July 2003 and March 2010 was conducted. ABI was measured using the automatic oscillometric method, and stratified into four groups: ABI ≤ 0.9 (low); 0.9 < ABI <1.0 (borderline low); 1.0 ≤ ABI <1.2 (normal); and 1.2 ≤ ABI <1.4 (high normal). RESULTS: In participants with ABI at least 1.0, ABI was positively correlated with SBP, pulse pressure, and brachial-ankle pulse wave velocity. In participants with ABI less than 1.0, all indices were negatively correlated with ABI. The prevalence of proteinuria, defined as ≥ 1+ by dipstick, was significantly higher in low (23%) and high normal ABI (10%) compared with borderline low (6%) and normal ABI (7%). In participants at least 60 years, proteinuria was significantly associated with only low ABI [odds ratio (OR) 3.22, 95% confidence interval 1.34-7.41] compared with normal ABI before and after multivariable adjustment. In participants less than 60 years, adjusted OR for proteinuria was only significantly associated with high normal ABI (OR 1.32, 95% confidence interval 1.01-1.74). CONCLUSION: High normal ABI in younger participants may be a result of arterial stiffness and associated with proteinuria.