Influence of baseline systolic blood pressure on the relationship between intensive blood pressure control and cardiovascular outcomes in the Systolic Blood Pressure Intervention Trial (SPRINT)

Visualizing Time-Varying Effect in Survival Analysis: 5 Complementary Plots to Kaplan-Meier Curve

Background

Kaplan-Meier (KM) curve has been widely used in the field of oxidative medicine and cellular longevity. However, time-varying effect might be presented in KM curve and cannot be intuitively observed. Complementary plots might promote clear insights in time-varying effect from KM curve.

Methods

Three KM curves were identified from published randomized control trials: (a) curves diverged immediately; (b) intersected curves with statistical significance; and (c) intersected curves without statistical significance. We reconstructed individual patient data, and plotted 5 complementary plots (difference in survival probability and risk difference, difference in restricted mean survival time, landmark analyses, and hazard ratio over time), along with KM curve.

Results

Entanglement and intersection of two KM curves would make the 5 complementary plots to fluctuate over time intuitively. Absolute effects were presented in the 3 plots of difference in survival probability, risk, and restricted mean survival time. Changed P values from landmark analyses were used to inspect conditional treatment effect; the turning points could be identified for further landmark analysis. When proportional hazard assumption was not met, estimated hazard ratio from traditional Cox regression was not appropriate, and time-varying hazard ratios could be presented instead of an average and single value.

Conclusions

The 5 complementary plots with KM curve give a broad and straightforward picture of potential time-varying effect. They will provide clear insight in treatment effect and assist clinicians to make decision comprehensively.

Antihypertensive treatment decrease stroke occurrence: a prospective cohort study

OBJECTIVE

Among the risk factors of stroke, hypertension was one of the most important and modifiable factors. The current study aimed to assess whether antihypertensive treatment to ideal levels of blood pressure can eliminate stroke risk in a prospective cohort study.

METHODS

The Kailuan study was a prospective longitudinal cohort study on stroke risk factors and events. We analyzed association of baseline antihypertensive treatment efficacy with the risk of stroke during 11.0-year follow-up, and further evaluated association of newly antihypertensive treatment efficacy at 4-year follow-up with subsequent stroke. Multivariate Cox proportion models were used to calculated hazard ratios and their 95% confidence intervals (CIs) for stroke.

RESULTS

A total of 97 772 participants (median age: 51.65 years) without previous stroke were included. At baseline, 55 518 participants had normotension, 2339 treated and controlled, 32 331 untreated hypertension and 7584 treated but uncontrolled. Compared with normotension, individuals with treated and controlled, untreated hypertension and treated but uncontrolled, had 83, 97 and 162% higher risk of developing total stroke after adjusting for potential stroke risk factors, respectively (hazard ratio 1.83 [95% CI 1.56-2.15], 1.97 [95% CI 1.85-2.11] and 2.62 [95% CI 2.40-2.86]; all P < 0.05). Whereas, normotension at baseline, who were newly normotension with antihypertensives at 4-year follow-up, exhibited no elevated total stroke risk (hazard ratio, 1.41 [95% CI 0.87-2.30]). Similar results existed for stroke subtypes (ischemic stroke and hemorrhagic stroke).

CONCLUSION

The data suggest that, antihypertensive treatment to normotensive individuals can reduce stroke risk in a short time.

Association between blood pressure levels and cardiovascular deaths: a 20-year follow-up study in rural China

OBJECTIVES

The 2017 American College of Cardiology/American Heart Association (ACC/AHA) hypertension guideline recommended 130/80 mm Hg as blood pressure (BP) target goals. However, the generalisability of this recommendation to populations at large with hypertension remains controversial. We assessed the association between BP and cardiovascular diseases (CVDs) mortality using a 20-year follow-up study among Chinese populations.

DESIGN

Prospective cohort study.

PARTICIPANTS

7314 participants were followed up for a median of 20 years in Fangshan District, Beijing, China.

METHODS

The primary outcome variable was death from cardiovascular causes. The adjusted HR for CVDs mortality associated with baseline BP was calculated using Cox regression analysis.

RESULTS

We identified 350 deaths from CVDs (148 stroke, 113 coronary heart disease and 89 other CVDs) during follow-up. Hypertension (defined by systolic BP (SBP)/diastolic BP (DBP) ≥140/90 mm Hg) was significantly associated with mortality due to CVDs (HR=2.49, 95% CI=1.77 to 3.50) among people aged 35-59 years rather than people aged ≥60 years. In addition, there was no significant association between stage 1 hypertension defined by the 2017 ACC/AHA (SBP/DBP of 130-139/80-89 mm Hg) and CVDs mortality when compared with SBP/DBP of <120/80 in neither the participants aged <60 years (HR=0.90, 95% CI=0.54 to 1.50) nor participants aged ≥60 years (HR=1.47, 95% CI=0.94 to 2.29).

CONCLUSION

The study revealed hypertension of SBP/DBP≥140/90 mm Hg was an important risk factor of CVDs mortality, especially among people aged 35-59 years. However, stage 1 hypertension under the definition of 2017 ACC/AHA was not associated with an increased risk of CVDs mortality. This study indicated that whether adopting the new hypertension definition needs further consideration in rural Chinese populations.