Visit-to-visit blood pressure variability and outcome: a traditional and a dose-response meta-analysis

It is not clear whether the relationship of blood pressure variability (BPV) with outcome reported in several studies is linear or becomes evident only above a given BPV threshold value. This meta-analysis was aimed at exploring the shape of the relationship between visit-to-visit BPV (VVBPV) and mortality or fatal and non-fatal cardiovascular events, also addressing whether the number of visits considered for estimation of VVBPV has an impact on this relationship.

Pooled hazard ratios and 95% confidence intervals for the association between VVBPV and outcomes were calculated by outcome type and number of visits used to estimate VVBPV. Restricted cubic spline meta-regression models were applied to explore the shape of this relationship and the presence of threshold values beyond which VVBPV significantly increases the risk of outcomes.

The literature search identified 50 studies (n=10,624,740 individuals). The risk of all-cause and cardiovascular mortality began to increase significantly above specific VVBPV threshold values. Systolic VVBPV measured as standard deviation (SD) had a threshold of 11.8 mmHg for all-cause mortality and 12.1 mmHg for cardiovascular mortality. Diastolic VVBPV SD showed threshold values of 5.8 mmHg for all-cause mortality and 5.25 mmHg for cardiovascular mortality, the risk of these outcomes increasing significantly only when VVBPV exceed these values. Our study also provides indications that a minimum of three visits is required to reliably assess the prognostic value of VVBPV.

This meta-analysis shows a non-linear dose-response relationship between VVBPV and outcomes, with distinct threshold values. The identification of such thresholds is vital for assessing the prognostic value of BPV in research or clinical settings. A reliable assessment of the prognostic value of VVBPV should be based on at least three visits.