Frequency of a low ankle brachial index in the general population by age, sex and deprivation: cross-sectional survey of 28 980 men and women

Objectives An increasing interest is observed in the use of the ankle brachial index (ABI, ratio of systolic blood pressure at the ankle to that in the arm) to assess cardiovascular risk. The aim of this study was to provide information on the distribution of ABI in a large healthy population, essential for planning implementation of ABI measurement in preventive strategies in the general population. Study design and setting Cross-sectional survey of the ABI was conducted in 28 980 men and women aged over 50 years, living in central Scotland and free of clinical cardiovascular disease. Results The ABI was approximately normally distributed in both men (mean 1.06, SD 0.13) and women (mean 1.01, SD 0.11). A total of 10.9% of participants had an ABI <= 0.90, the most common cutpoint used to indicate increased cardiovascular risk. This percentage was higher for women (13.6%) than for men (73%) and rose with increasing age and with increased deprivation (6.7% in most affluent and 14.4% in most deprived participants). Similar patterns were observed for various different ABI cutpoints (<= 0.85, <= 0.95 and <= 1.0), the use of which (as expected) had a major influence on the proportion of the population categorized as 'at risk'. Conclusions Careful consideration is required of any ABI cutpoint used to discriminate between participants at 'high' and 'low' risk of cardiovascular disease, in terms of the proportion of the population who might then qualify for preventive measures. It may also be necessary to consider different cutpoints for men and women and for different age categories.