To assess the effect of blood pressure lowering treatment on the risk of death and cardiovascular disease at different blood pressure levels.Design and method:
We used data from a previous systematic review and meta-analysis of blood pressure lowering treatment, adding the results from the recently published HOPE-3 trial. The previous review standardised risk ratio and study weights according to blood pressure lowering, which has previously been associated with deranged results. We re-analysed data using non-standardised methods and explored reasons for heterogeneity when present.Results:
We included 60 trials, including 295 002 patients, in our meta-analyses. The relative risk reduction with blood pressure lowering was attenuated at lower baseline systolic blood pressure (p < 0.001 for mortality, major cardiovascular events, stroke and heart failure). Antihypertensive treatment reduced the risk of death only if baseline systolic blood pressure was >150 mmHg (RR 0.87, 95 % CI 0.80–0.95 if SBP 150–159 mmHg, compared to RR 1.01, 0.96–1.07 if SBP 140–149 mmHg). For major cardiovascular events a beneficial effect was seen across blood pressure strata, but the benefit was significantly smaller at lower blood pressure levels (RR 0.92, 0.87–0.98 if SBP 130–139 mmHg, compared to 0.75, 0.67–0.84 if SBP > 160 mmHg). We observed significant heterogeneity in the 130–139 and 140–149 mmHg blood pressure strata in the major cardiovascular event analysis (I2 59 %, p = 0.001 respectively I2 65 %, p = 0.005). The heterogeneity disappeared when analyses were restricted to trials without previous cardiovascular disease. In trials with a baseline systolic blood pressure <140 mmHg, treatment reduced the risk of major cardiovascular events only in patients with pre-existing disease (RR 0.84, 0.80–0.89), whereas treatment effect was neutral in primary preventive trials (RR 0.98, 0.94–1.02, p < 0.001 for interaction).Conclusions:
The effect of blood pressure lowering on mortality and cardiovascular disease is modified by baseline systolic blood pressure and pre-existing cardiovascular disease. If cardiovascular disease is present, blood pressure lowering is beneficial across all blood pressure levels. Without cardiovascular disease, however, there is no benefit with treatment < 140 mmHg.