The significance of combining inter-limb blood pressure differences in predicting the future cardiovascular risk in elder chinese: the northern shanghai study

Objective: The three indexes derived from the inter-limb systolic blood pressure difference (ISBPD), namely inter-arm (IASBPD) and -leg (ILSBPD) systolic blood pressure differences and ankle-brachial index (ABI), were proved associated with cardiovascular morbidity and mortality, respectively. Whether the combination of the three indexes can improve the prediction of future cardiovascular risk remains unclear. We aimed to explore the clinical significance of combining IASBPD, ILSBPD, and ABI in predicting future cardiovascular risk in a large cohort of elderly Chinese. Design and method: A total of 3095 participants (mean age: 71±6 years) derived from the Northern Shanghai Study were included in the present analysis. According to the number of abnormal ISBPDs (IASBPD> = 20 mmHg, ILSBPD> = 20 mmHg, and ABI< = 0.9), the participants were divided into three groups: Group 0 (without abnormal ISBPD, n = 2507), 1 (with 1 abnormal ISBPD, n = 418), and 2 (with> = 2 ISBPDs, n = 170). The study endpoint was defined as the composite major adverse cardiovascular events (MACEs) including non-fatal myocardial infarction (MI), and non-fatal stroke, and all-cause mortality. Survival analysis and Cox proportional hazards models were performed to compare the rates of the endpoint between groups. The discriminative ability of ISBPDs and ABI was compared using R 2 , C-index, NRI, and IDI. Results: During a median follow-up period of 5.4 years (interquartile range 4.4-7.3 years), 325 events (10.5%) were observed, with 40 non-fatal MI, 101 non-fatal stroke, and 205 deaths. Survival Analysis indicated the highest rates of the endpoint in Group 2, followed by Group 1 and Group 0 (P<0.001). In Cox regression model, after adjustment for possible confounding factors, Group 2 showed significantly higher risk of events than that of Group 0 (HR: 1.50, 95% CI: 1.06-2.13); Group 1 also showed higher risk of events compared to Group 0, but did not reach statistical significance (HR: 1.25; 95%CI: 0.94 to 1.65). The addition of IASBPD and ILSBPD on ABI improved the prediction of cardiovascular risk (net reclassification improvement 4%,95%CI: -0.05 to 0.13), after adjusted for potential confounders. Conclusions: The combination of ISBPDs may help to better predict the future cardiovascular risk in the elderly.