Systolic inter-arm differences in blood pressure have been associated with all-cause mortality
and cardiovascular disease. We undertook individual participant data meta-analyses to 1)
quantify independent associations of systolic inter-arm difference with mortality and
cardiovascular events; 2) develop and validate prognostic models ...
Systolic inter-arm differences in blood pressure have been associated with all-cause mortality
and cardiovascular disease. We undertook individual participant data meta-analyses to 1)
quantify independent associations of systolic inter-arm difference with mortality and
cardiovascular events; 2) develop and validate prognostic models incorporating inter-arm
difference, and 3) determine whether inter-arm difference remains associated with risk after
adjustment for common cardiovascular risk scores. We searched for studies recording bilateral
blood pressure and outcomes, established agreements with collaborating authors, and created
a single international dataset (the INTERPRESS-IPD Collaboration). Data were merged from 24
studies (53,827 participants). Systolic inter-arm difference was associated with all-cause and
cardiovascular mortality: continuous hazard ratios 1.05 (95% confidence interval 1.02 to; 1.08)
and 1.06 (95% confidence interval 1.02 to 1.11) respectively per 5 mmHg systolic inter-arm
difference. Hazard ratios for all-cause mortality increased with inter-arm difference magnitude
from a ≥5 mmHg threshold (hazard ratio 1.07; 95% confidence interval 1.01 to 1.14). Systolic
inter-arm differences per 5 mmHg were associated with cardiovascular events in people
without pre-existing disease, after adjustment for ASCVD (hazard ratio 1.04; 95% confidence
interval 1.00 to 1.08), Framingham (hazard ratio 1.04; 95% confidence interval 1.01 to 1.08), or
QRISK2 (hazard ratio 1.12; 95% confidence interval 1.06 to 1.18) cardiovascular risk scores. Our
findings confirm that systolic inter-arm difference is associated with increased all-cause
mortality, cardiovascular mortality, and cardiovascular events. Blood pressure should be
measured in both arms during cardiovascular assessment. A systolic inter-arm difference of 10
mmHg is proposed as the upper limit of normal.
