24-h ambulatory blood pressure versus clinic blood pressure as predictors of cardiovascular risk: a systematic review and meta-analysis of prospective studies

BACKGROUND: There is uncertainty about the usefulness of ambulatory blood pressure (ABP) in predicting cardiovascular disease (CVD) risk. Our objective was to compare the prognostic value of ABP versus clinic blood pressure (BP) in CVD. METHODS: We conducted electronic searches on Medline, Embase, and the Cochrane library up to July 2018. We included prospective longitudinal studies that compared 24-h ABP with clinic BP measurement in adults. Our main outcomes were all-cause mortality, CVD mortality, and/or CVD events. We assessed study quality based on four domains and pooled data using a random effects model of STATA for meta-analyses. RESULTS: We included 13 studies comprising 81 736 participants. The overall quality of the studies was moderate. Both systolic and diastolic 24-h ABP as well as systolic clinic BP significantly predicted all-cause mortality, CVD mortality, and CVD events. Systolic 24-h ABP was significantly better than systolic clinic BP at predicting future risk of CVD events: combined hazard ratio for 24-h ABP = 1.27 (95% confidence interval 1.21-1.34) per 10 mmHg increase in SBP compared with 1.13 (1.06-1.21) for clinic BP (interaction test P = 0.02). After adjusting for clinic BP, both systolic and diastolic 24-h ABP measurements were significantly better than their corresponding clinic measurements at predicting all-cause mortality, CVD mortality, and CVD events (P = 0.001 and P = 0.000, respectively). CONCLUSION: Systolic 24-h ABP is a better predictor of future CVD events than systolic clinic BP. Future studies should incorporate the use of individual patient data to assess the prognostic value of 24-h ABP.