Interarm differences in seated systolic and diastolic blood pressure: the Hypertension Genetic Epidemiology Network study

OBJECTIVE: To examine whether blood pressure (BP) differs between arms in hypertensive siblings and randomly selected volunteers, and whether this difference is explained by cardiovascular risk factors. METHODS: The Hypertension Genetic Epidemiology Network recruited 2395 hypertensive siblings and 854 volunteers. BP was measured six times (three measurements per arm) in seated participants using a Dinamap monitor. The average of three measurements was calculated per arm and the difference taken between arms (i.e. interarm BP differences). RESULTS: The mean age of the subjects was 56 years, and about one-half of the sample was male. More than one-half of the sample was African-American. The mean diastolic BP was equal in the two arms in the random sample (68.8 versus 68.7 mmHg) and in hypertensive siblings (73.4 versus 73.1 mmHg), as was systolic BP (random, 119.6 versus 119.3 mmHg; hypertensives, 130.8 versus 130.7 mmHg). The mean interarm diastolic and systolic BP differences were 2.96 +/- 2.51 and 4.61 +/- 4.10 mmHg, respectively, in the random sample and were 3.09 +/- 2.73 and 5.35 +/- 4.98 mmHg, respectively, in hypertensive siblings. Few (random, 1.6%; hypertensives, 2.8%) had interarm diastolic BP differences > 10 mmHg, but 9.2% of the random sample and 14.2% of hypertensive siblings had systolic BP differences > 10 mmHg. Obesity, higher heart rate, and higher systolic BP were associated with larger interarm BP differences. These results have implications for blood pressure measurement in research settings and in screening programs.