Hypertension Screening for Cardiovascular Health
Introduction
Hypertension is a contributing risk factor for cardiovascular health. In the recent European Society of Cardiology (ESC) guidelines, the main recommendation for antihypertensive treatment of patients was regarded by the future risk of cardiovascular (CV) mortality, CV disease, or total mortality. The guideline state that the decision on treatment should be according to risk estimates over 10 years. In the 1970s and early 1980s, diastolic blood pressure (DBP) was regarded as superior to systolic blood pressure (SBP) to estimate future cardiovascular health.
Later studies have challenged the importance of DBP in predicting coronary heart disease (CHD). Along this line, Framingham Study data have indicated that SBP was superior to DBP for estimating future risk. In particular, studies of the elderly have reported the importance of SBP. A new study of adults reveals both systolic and diastolic blood pressures have great adverse effects on future cardiovascular health. A study was performed on a population of 70–78-year-old in the Netherlands based on survival analysis approaches.
Overview of the Study
This study was designed to study whether SBP adds prognostic information to DBP and whether both 24-h ambulatory SBP and 24-h ambulatory DBP are specifically important for cardiovascular health.
Methods
The researchers examined 2097 participants from a population cohort recruited in Copenhagen, Denmark. Cause-specific Cox regression was performed to predict 10-year person-specific absolute risks of fatal and non-fatal cardiovascular (CV) events. Also, the time-dependent area under the receiver operator curve (AUC) was utilized to evaluate discriminative ability. The calibration plots of the models (Hosmer-May test) were calculated as well as the Brier score which combines (discrimination and calibration).
At enrolment, BP measurements, including ambulatory SBP and DBP measurements during a 24-h period and office BP were registered. Additionally, the recorded data information consisted of baseline risk factors of CV outcomes and follow-up information on CV events of participants. The participants’ information about baseline CV risk factors was obtained with questionnaires.9 Information about treatment for antihypertensive drugs, history of CVD, and diabetes were registered.
The condition of fatal and non-fatal complications and survival status were reported based on registered follow-up. The main outcomes were CV mortality and CV events. The CV events included both fatal and non-fatal CV complications.
The combination of fatal and non-fatal CV events was considered cerebrovascular death and non-fatal stroke; coronary events (death from ischemic heart disease, sudden death, non-fatal myocardial infarction, or coronary revascularization). Also, cardiac events were specified as fatal or non-fatal heart failure and coronary events. Moreover, each of the aforementioned fatal and nonfatal CV events individually was done as the secondary outcome.
Results
In this study, the findings show that (I) adding 24-h ambulatory SBP to 24-h ambulatory DBP does not provide any extra prognostic information for 10-year person-specific absolute risks of CV complications (II) adding office SBP to office DBP does not obtain additional predictive accuracy for 10-year risks of CV events.
The difference in AUC (95% confidence interval; p-value) was .26% (-.2% to .73%; .27) for 10-year CV mortality and .69% (-.09% to 1.46%; .082) for 10-year risk of CV events. The difference in AUC was .12% (-.2% to .44%; .46) for 10-year CV mortality and .04% (-.35 to .42%; .85) for 10-year risk of CV events. Moreover, for both CV mortality and CV events, office SBP did not improve prognostic information to office DBP. In addition, the Brier scores of office BP in both CV mortality and CV events were .078 and .077, respectively.
Furthermore, the Brier scores were .077 and .078 in CV mortality and CV events of the 24-h ambulatory. For the average population as those participating in a population survey, the 10-year discriminative ability for long-term predictions of CV death and CV events is not improved by adding systolic to diastolic blood pressure. This finding is found for ambulatory as well as office blood pressure.
Conclusion
It is concluded from the findings of this study that adding SBP to DBP does not improve the 10-year predictions of fatal and non-fatal CV events for both 24-h ambulatory BP and office BP. Previous studies focused on estimating hazard ratios using Cox models. These methods have some fundamental weaknesses, including choosing one important variable between two correlated variables and ignoring the distribution of events during the follow-up by using average HR. For these reasons, it seems that using a more advanced model is necessary to estimate person-specific predicted 10-year risks and cause-specific hazard ratios. Also, a few studies have been done based on discriminative ability to assess predictive performance. This long-term risk prediction of person-specific is related to both approaches, including non-CV mortality in competing risk and the relationship between BP and CV event. The present study obtained the hazard ratios using cause-specific cox regression and considered person-specific predictions for 10-year absolute risks of CV outcomes. Moreover, the current cohort study assessed the statistical significance of hazard ratios and the predictive accuracy of long-term person-specific cardiovascular health predictions.
Although high significant hazard ratios, it does not lead to substantial changes for long-term predictions. According to the findings, the prognostic information for assessing the 10-year risk of CV complications is not improved by adding 24-h ambulatory SBP to 24-h ambulatory DBP, and also adding office SBP to office DBP is to absolute risks obtained by office DBP alone.
In both comparisons, the prognosis information does not change when the information of SBP is added to DBP in a greater number of persons. The results indicate the application of discriminative ability by using a time-dependent area under the receiver operating characteristic curve (AUC) for competing for risks to evaluate predictive accuracy.
Despite high hazard ratios in the cause-specific Cox regression model, the effects do not change into statistically significant improvements for long-term person-specific predictions. The concept of AUC is the probability that an individual who experiences the CV events or CV mortality received a higher predicted 10-year risk than an individual who was alive 10 years after the BP measurements or died due to non-CV causes. Based on the results, 24-h ambulatory SBP is not able to add additional prognostic information to 24-h ambulatory DBP using time-dependent AUC of discrimination ability in both CV mortality and CV events (Table 2). Also, office SBP cannot add prognostic information to office DBP in CV mortality and CV events
This study can calculate the long-term risk predictions of individuals. The research also takes a step further by evaluating the cause-specific Cox regression model to predict 10-year person-specific absolute risks of CV events.
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