Age- and sex-related effects on ankle-brachial index in a screened cohort of Japanese: the Okinawa Peripheral Arterial Disease Study (OPADS).

AIMS: Age-related change of ankle-brachial index (ABI) within the general population, especially <40 years, has not been determined in large population studies. We evaluated the value of the ABI by age- and sex-related differences in a screened cohort.

METHODS AND RESULTS: The ABI was examined in 13,211 participants (aged 21-89 years) in a health evaluation programme. The mean ABI was lower in women than in men at all ages. The ABI was lowest at <40 years, and increased with age; the maximum was at 60-69 years in both sexes. In participants <40 years, 186 (22%) of women and 108 (9.8%) of men had a borderline ABI (0.9-1.0). The prevalence of an ABI ≤0.9 in men increased with age, and sharply rose to 3.3% at ≥70 years. Conversely, women demonstrated a J-curve relationship, where the prevalence of an ABI ≤0.9 was lowest at 60-69 years (0.2%), and increased at <40 (0.9%) and ≥70 years (1.6%). The prevalence of atherosclerotic risk factors was higher in participants with an ABI ≤0.9 than those with an ABI >0.9 in men, both ≤60 and >60 years, and in women >60 years. In women ≤60 years, however, the prevalence of atherosclerotic risk factors in participants with an ABI >0.9 was as small as those with an ABI ≤0.9.

CONCLUSION: The ABI increased with age until 60-69 years, and was lower in women than in men. It is unlikely that a low ABI in younger healthy women always indicate that existence of arterial stenosis.