A new study has found that both systolic and diastolic blood pressure independently influenced the risk of adverse cardiovascular events.
Despite being researched for decades, the effect of systolic and diastolic blood pressure on cardiovascular outcomes has remained unclear, but a recent study could offer physicians a greater insight into their impact.
After examining data from more than 1.3 million adults patients, a team of investigators from Kaiser Permanente, Brigham and Women’s Hospital, and Harvard Medical School found that both systolic and diastolic hypertension independently influenced the risk of adverse cardiovascular events, regardless of the definition of hypertension. Additionally, investigators noted that elevated systolic blood pressure had a greater effect on outcomes.
On the heels of recently revised guidelines with 2 different thresholds for treatment of hypertension, investigators set out to evaluate whether systolic and diastolic hypertension independently influence the risk of adverse cardiovascular outcomes. Using outpatients from Kaiser Permanente Northern California, investigators carried out a retrospective cohort study that included 1,316,363 patients.
The primary outcome of the study was a composite of the first episode of myocardial infarction (MI), ischemic stroke, or hemorrhagic stroke during the study period. Investigators defined an event as hospitalization with a discharge diagnosis matching one of the components of the primary endpoint.
Investigators included all outpatient blood pressure measurement for all participants in the analyses — this includes measurements from both the baseline and observation period, up to a composite outcome event. Covariates of the study were sex, age, race or ethnic group, BMI, and coexisting conditions.
A bivariate and multivariable Cox survival analysis of the composite outcome performed using z-score-standardized hypertension-burden predictors as the primary analysis for the study.
Upon analysis, investigators identified a total of 44,286 outcome events — this includes 24,681 MI, 16,271 ischemic stroke, and 3334 hemorrhagic strokes. In survival models, investigators noted a continuous burden of systolic hypertension (≥140 mm Hg; HR per unit increase in z score, 1.18; 95% CI, 1.17 to 1.18) and diastolic hypertension (≥90 mm Hg; HR per unit increase in z score, 1.06; 95% CI, 1.06 to 1.07) independently predicted the composite outcome.
Additionally, results remained similar when using the lower threshold of hypertension and with systolic and diastolic used as predictors without hypertension thresholds. Investigators observed a J-curve relation between diastolic blood pressure and outcomes — this was explained in part by age and other covariates and by a higher effect of systolic hypertension in patients within the lowest quartile of diastolic blood pressure.
In an interview with MD Magazine®, study investigator Deepak Bhatt, MD, MPH, executive director of Interventional Cardiovascular Programs at Brigham and Women's Hospital and professor of medicine at Harvard Medical School, said the results demonstrate the importance of both systolic and diastolic blood pressure.
“Controversy has long persisted about whether systolic blood pressure, diastolic blood pressure, or both contribute to cardiovascular risk. This analysis convincingly demonstrates that both are important, and it shows that in people who are otherwise generally healthy, the lower the blood pressure, the better,” Bhatt explained. “These findings are supportive of the NIH-sponsored SPRINT trial results and are in keeping with the latest recommendations from the ACC/AHA guidelines. Additionally, this study provides a very clinically useful application of “big data,” with over 36 million blood pressures from over 1 million Kaiser patients analyzed.”
This study, titled “Effect of Systolic and Diastolic Blood Pressure on Cardiovascular Outcomes,” is published in The New England Journal of Medicine.