Interarm blood pressure difference and risk assessment: the ECHORN cohort study

Background Guidelines recommend measuring blood pressure (BP) in both arms and using the higher reading. Aim To determine interarm pressure difference (IAD) distribution and associated factors, and BP and atherosclerotic cardiovascular disease (ASCVD) risk classification using the higher and lower readings. Design & setting This cohort study used a representative cross-sectional sample of community-dwelling residents aged ≥40 years on four Caribbean islands (Barbados, Puerto Rico, US Virgin Islands, and Trinidad). Method BP was measured simultaneously in both arms. Mixed effects logistic and linear regression tested associations with an IAD. BP and ASCVD risk were classified using the higher and lower BP. Results Of 2912 participants (mean age 57.2 years), 10.7% (95% confidence interval [CI] = 9.6 to 11.8) and 3.3% (95% CI = 2.6 to 3.9) had systolic IADs ≥10 mmHg and ≥15 mmHg, respectively, and 5.0% (95% CI = 4.2 to 5.8) and 1.8% (95% CI = 1.3 to 2.3) diastolic IADs ≥10 mmHg and ≥15 mmHg, respectively. Independent associations with systolic and diastolic IADs ≥10 mmHg and/or continuous outcomes, included increasing body mass index (BMI), systolic and diastolic pressures and hypertension ( P <0.05). Higher versus lower arm BP reclassified 10.3% (95% CI = 7.8 to 12.8) and 8.3% (95% CI = 5.9 to 10.7) from below to above the 130-mmHg and 140-mmHg systolic thresholds, respectively, 10.8% (95% CI = 8.2 to 13.3) and 6.9% (95% CI = 4.9 to 8.9) at the 80-mmHg and 90-mmHg diastolic thresholds, respectively, and 9.2% (95% CI = 0.0 to 18.4) of those with an IAD of ≥10 mmHg at the ≥10% 10-year ASCVD risk threshold. Conclusion Assessing both arms detects an IAD ≥10 mmHg and reclassifies BP in about 1 in 10 people. Increasing BMI and BP increase the risk of an IAD ≥10 mmHg or 15 mmHg.