Association between high-normal ankle-brachial index and hypertension incidence: the Okinawa Peripheral Arterial Disease Study.

Abstract

Arterial stiffness is associated with longitudinal increases in blood pressure and hypertension development. A screened cohort was used to test whether increases in the ankle-brachial index (ABI) with age occur as a result of increasing arterial stiffness and wave reflection and is associated with hypertension incidence. We analysed the data of 1344 participants without hypertension at baseline who underwent ABI measurements at least twice with an interval of at least 36 months. Participants with abnormal ABI values were excluded. The median age of participants was 51 years (55% women). The ABI was lowest for participants younger than 40 years and increased with age. At the time of the follow-up visit (median follow-up period, 47 months), 224 (17%) participants had developed hypertension. Multiple linear regression analysis revealed that baseline ABI was positively and independently associated with the yearly change in brachial SBP and hypertension incidence. Compared with participants with a normal ABI (1.00-1.19), the adjusted odds ratio for hypertension incidence was significantly higher for participants with a high-normal ABI (1.20-1.39) before and after multivariate adjustment for conventional risk factors (odds ratio, 2.17, 95% confidence interval 1.20-3.95). Addition of ABI to a model containing conventional risk factors did not improve the c-statistics but the net reclassification index of ABI was 0.17 (95% confidence index 0.01-0.37) for hypertension incidence. Baseline ABI was positively and independently associated with the yearly change in SBP and hypertension incidence.