Ankle Blood Pressure Corresponding to Brachial Blood Pressure: Age- and Sex-Specific Reference Values

Background Brachial blood pressure (BP) measurement is the standard method for diagnosing hypertension, but alternative measurement sites, like the ankle, may be needed in certain clinical cases. Current guidelines lack age- and sex-specific reference values for these measurements, which may lead to misdiagnosis. This study investigates variations in supine ankle BP across different ages and sexes at equivalent seated brachial BP levels.Methods This study utilized health examination data from 102,956 adults aged 20-79 years between 2010 and 2019. Participants with ankle-brachial index (ABI) outside the normal range of 0.91-1.4 or histories of cardiovascular disease, stroke, or malignancy were excluded. BP measurements followed a standardized protocol with validated devices. Supine ankle BP was compared with seated brachial BP across age and sex groups.Results Of the 102,956 participants, 32,416 were women (mean age 41.5 years) and 70,540 were men (mean age 43.5 years). Supine ankle BP readings consistently increased with age and were higher in men than women at equivalent seated brachial BP levels. At a seated brachial BP of 130/80 mm Hg, supine ankle BP increased from 142/75 mm Hg in women in their 20s to 162/82 mm Hg in their 70s, and from 146/79 mm Hg to 164/83 mm Hg in men over the same age range.Conclusions Supine ankle BP increases with age and is higher in men than women at equivalent seated brachial BP levels. These age- and sex-specific reference values enhance the accuracy of hypertension diagnosis when brachial BP measurement is impractical.