Abstract P514: Age-related Differences in the Annual Changes of the Ankle-brachial Pressure Index: Underlying Mechanisms

Abstract

Objectives: The present prospective observational study was conducted to examine the age-related annual changes of the ankle-brachial pressure index (ABI) and their association with the longitudinal changes of the brachial-ankle pulse wave velocity (baPWV), a marker of arterial stiffness, and the radial augmentation index (rAI), a marker of the pressure wave reflection in middle-aged Japanese men. Methods and Results: In 4264 men (42 ± 9 years old) of a Japanese construction company, the ABI, baPWV and rAI were measured annually over a 9-year observation period. During the study period, ABI (from 1.10 ± 0.07 to 1.13 ± 0.07), baPWV (from 1295 ± 194 to 1344 ± 217 cm/sec) and rAI (from 69 ± 13 to 72 ± 13 %) were increased significantly (p<0.01). Mixed model linear regression analysis of the repeated-measures data revealed that the annual increase of the ABI was lower in men aged over 50 years of age (n = 1237: 0.28 ± 0.06) than in those aged under 50 years of age (n = 3027: 0.50 ± 0.04) (p < 0.01). Furthermore, while increased baPWV (estimate = 0.017, p < 0.05) and increased rAI (estimate 0.254, p < 0.05) were significantly related to the annual increase of the ABI in men aged <50 years (p < 0.01), no such association was observed in men aged > 50 years. Conclusion: In middle-aged Japanese men, the ABI increases with age until the age of 50 years, and increased arterial stiffness and increased pressure wave reflection may contribute to this annual increase. In men aged > 50 years, the annual increase of the ABI was attenuated, which could be related, at least in part, to the attenuation of the increase of the pressure wave reflection and also attenuation of the effect of increased arterial stiffness on the hydrostatic pressure in the arteries with age. These findings may suggest the usefulness of ABI measurement as a screening tool for peripheral arterial disease in men over 50 years old.