INTER-ARM BLOOD PRESSURE DIFFERENCE

Abstract

Objective: Differences in systolic blood pressure (BP) between arms are associated with excess mortality and cardiovascular events. Inter-arm difference (IAD) has been attributed to both subclavian stenosis and to arterial stiffening, however the patho-physiological basis of IAD has not been established. We explored cross-sectional associations of systolic IAD (sIAD) within the INTERPRESS individual participant data (IPD) Collaboration to gain further insight. Design and method: The INTERPRESS-IPD Collaboration pooled records for 57,434 participants across 24 studies from Europe, North America, East Asia and Africa. We used hierarchical IPD linear regression with random effects for study, to perform univariable and multivariable models, examining cross-sectional associations of sIAD with known markers of cardiovascular risk. IAD was based on a single pair of BP readings. Models were compared using Aikeke's information criterion (AIC) and likelihood ratios (LR). Analyses were undertaken using Stata v15.0. Results: Complete data existed for 43,488 participants from 22 cohorts. Ankle brachial index (ABI) was negatively correlated with sIAD: coefficient −0.69 mmHg per 0.1 increment of ABI (−0.65 to −0.4; p < 0.001; figure). On multivariable modelling, magnitude of sIAD was positively associated with smoking (p = 0.04), age (p = 0.05), body mass index (p < 0.001), and systolic BP (p < 0.001). sIAD was lower for African American (p = 0.04) and Hispanic American (p < 0.01) participants compared to White ethnicity, and lower for men than women (p = 0.02). Using all available case data then multivariable model was confirmed. Goodness of fit improved on taking account of pre-existing cardiovascular disease (LR p = 0.004; n = 41,664), with addition of pulse pressure (LR p < 0.001; n = 33,844) or on adjustment for renal disease (LR p < 0.001; n = 15,541). AIC was non-discriminatory between models.Conclusions: This large multivariable analysis confirms the independent association of sIAD with recognised cardiovascular risk markers normally associated both arterial stiffening and with occlusive arterial disease. It is likely that both conditions make a contribution to the aetiology of IAD. These findings can support further hypothesis generation and study design.