Results
Using BP measurements at baseline, we categorized the 2 196 437 participants as having normal BP (n=1 155, 885), elevated BP (n=337 390), stage 1 hypertension (n=459 820), or stage 2 hypertension (n=243 342). Participants with elevated BP, stage 1 hypertension, and stage 2 hypertension were older and more likely to be men than their counterparts with normal BP (
Table). At baseline, participants in the elevated BP and stage 1 and stage 2 hypertension groups had higher body mass index, waist circumference, plasma glucose, hemoglobin A
1c, and serum low-density lipoprotein cholesterol and triglyceride levels and lower serum high-density lipoprotein cholesterol levels compared with the normal BP group. Cigarette smoking and alcohol consumption were more common in participants in the elevated BP and stage 1 and stage 2 hypertension groups compared with the normal BP group.
During a mean follow-up of 1112±854 days, 28 056 HF and 7774 AF events occurred. The cumulative incidence of HF and AF events was lowest in the normal BP group, followed by the elevated BP group, the stage 1 hypertension group, and the stage 2 hypertension group (
Figure 1). The event rates for HF and AF events were lowest in the normal BP group (2.99 and 0.78, respectively, per 1000 person-years), followed by the elevated BP group (3.56 and 1.04, respectively, per 1000 person-years), the stage 1 hypertension group (5.00 and 1.54, respectively, per 1000 person-years), and the stage 2 hypertension group (9.53 and 2.41, respectively, per 1000 person-years). In an unadjusted model, elevated BP, stage 1 hypertension, and stage 2 hypertension were associated with a significantly higher risk of HF and AF events compared with normal BP. After multivariable adjustment, the hazard ratios for HF and AF events were 1.10 (95% CI, 1.05–1.15) and 1.07 (95% CI, 0.99–1.17), respectively, for elevated BP; 1.30 (95% CI, 1.26–1.35) and 1.21 (95% CI, 1.13–1.29), respectively, for stage 1 hypertension; and 2.05 (95% CI, 1.97–2.13) and 1.52 (95% CI, 1.41–1.64), respectively, for stage 2 hypertension (
Figure 2). We assessed the proportional hazards assumptions by graphically checking log-log plots and did not find any obvious violation of the assumption. Each 1 SD higher SBP (per 15.9 mm Hg) and DBP (per 11.6 mm Hg) were associated with a higher risk for HF and AF events (
Table II in the Data Supplement). The PAFs for HF associated with stage 1 hypertension and stage 2 hypertension were 6.1% (95% CI, 5.4%–6.8%) and 11.9% (95% CI, 11.5%–12.4%), respectively. The PAFs for AF associated with stage 1 hypertension and stage 2 hypertension were 5.1% (95% CI, 3.4%–6.7%) and 7.5% (95% CI, 6.4%–8.6%), respectively.
During the follow-up, 3540 MI, 30 858 AP, and 13 401 stroke events occurred. The cumulative incidence of MI, AP, stroke, and composite CVD events was highest in the stage 2 hypertension group, followed by the stage 1 hypertension group, elevated BP group, and normal BP group (
Figure 1). In adjusted models, elevated BP, stage 1 hypertension, and stage 2 hypertension versus normal BP were each associated with a significantly higher risk for MI, AP, stroke, and composite CVD events (
Figure 2). We assessed the proportional hazards assumptions by graphically checking log-log plots and did not find any obvious violation of the assumption. Each 1 SD higher SBP and DBP were associated with a higher risk for MI, AP, stroke, and composite CVD events (
Table II in the Data Supplement). The PAFs for MI associated with stage 1 hypertension and stage 2 hypertension were 9.6% (95% CI, 7.5%–11.8%) and 11.8% (95% CI, 10.4%–13.2%), respectively. The PAFs for AP associated with stage 1 hypertension and stage 2 hypertension were 4.4% (95% CI, 3.7%–5.2%) and 6.8% (95% CI, 6.3%–7.3%), respectively. The PAFs for stroke associated with stage 1 hypertension and stage 2 hypertension were 7.0% (95% CI, 5.9%–8.0%) and 13.1% (95% CI, 12.5%–13.8%), respectively. Last, the PAFs for composite CVD end point associated with stage 1 hypertension and stage 2 hypertension were 5.4% (95% CI, 4.9%–5.9%) and 9.4% (95% CI, 9.1%–9.7%), respectively.
Sensitivity Analyses
We imputed missing data for covariates (left column in the Table). Results with versus without multiple imputation for missing covariates were similar in terms of the point estimates for elevated BP, stage 1 hypertension, and stage 2 hypertension (
Table III in the Data Supplement). When we adjusted for glucose and lipid parameters as continuous variables instead of categorial variables, results were similar in terms of the point estimates for elevated BP, stage 1 hypertension, and stage 2 hypertension for each CVD event (
Table IV in the Data Supplement). The point estimates for each CVD event associated with stage 2 hypertension when participants taking antihypertensive medication were included versus not included were similar (
Table V in the Data Supplement). We analyzed the relationship between the BP category according to the average of 2 BP measurements and the incidence of CVD from the time point 1 year after the 1st BP evaluation. As
Table VI in the Data Supplement shows, the results of this sensitivity analysis were also consistent with our main results, and stage 1 hypertension was associated with higher incidence of HF and AF. We calculated cause-specific hazard ratios to account for the competing risk of death as shown in
Table VII in the Data Supplement. The results with and without using competing-risk models were similar in terms of the point estimates for risks of CVD events for each BP group.
Discussion
The present analyses using a nationwide epidemiological database, including a general population of >2 million adults without a history of CVD, demonstrated that stage 1 hypertension and stage 2 hypertension, as defined by the 2017 ACC/AHA BP guideline, were associated with a higher risk for subsequent HF, AF, MI, AP, and stroke. Elevated BP was also associated with a higher risk for subsequent HF, MI, AP, and stroke. PAFs for HF, AF, MI, AP, and stroke associated with stage 1 hypertension were 6.1%, 5.1%, 9.6%, 4.4%, and 7.0%, respectively. PAFs for HF, AF, MI, AP, and stroke associated with stage 2 hypertension were 11.9%, 7.5%, 11.8%, 6.8%, and 13.1%, respectively.
Lowering the BP threshold for the diagnosis of hypertension by 10 mm Hg in the 2017 ACC/AHA BP guideline was a bold revision with major medical and public health implications. Clinical evidence supporting the validity of the 2017 ACC/AHA BP guideline is still accruing. From this perspective, our results using a large-scale epidemiological database and showing the association between stage 1 hypertension and higher incidence of HF, AF, and other CVDs support the validity of this decision.
Individuals with elevated BP or stage 1 hypertension are at high risk for developing stage 2 hypertension,
25 and those with stage 1 hypertension who experienced an increase in SBP/DBP to ≥140/90 mm Hg have a 3-fold higher incidence of CVD events compared with those who maintain SBP/DBP <130/<80 mm Hg,
26 In this regard, 3 previous randomized clinical trials have suggested the efficacy of pharmacological treatment in the prevention of stage 2 hypertension among individuals with elevated BP or stage 1 hypertension.
27–29In the PREVER-Prevention trial (Prevention of Hypertension in Patients With Prehypertension), low doses of a thiazide-type diuretic combined with a potassium-sparing agent prevented the incidence of stage 2 hypertension by almost 50% among individuals with elevated BP or stage 1 hypertension.
27 Left ventricular mass assessed through Sokolow-Lyon voltage and voltage-duration product decreased to a greater extent in participants allocated to the intervention group compared with the placebo group. These results suggest that preventing progression to stage 2 hypertension could reduce the burden of high BP among individuals with elevated BP or stage 1 hypertension, which may lead to a reduced lifetime risk of CVD. Similarly, TROPHY (Trial of Preventing Hypertension) showed that treatment with angiotensin receptor blocker for subjects with stage 1 hypertension was well tolerated and reduced the risk of the development of hypertension.
28 Furthermore, the PHARAO study (Prevention of Hypertension With the Angiotensin Converting Enzyme Inhibitor Ramipril in Patients With High-Normal Blood Pressure) demonstrated that treatment with an angiotensin-converting enzyme inhibitor for subjects with high-normal office BP could lower the risk of progression to manifest hypertension compared with a control group.
29The optimal treatment strategy may vary depending on the CVD risk of each individual. The 2017 ACC/AHA BP guideline recommends the combination of nonpharmacological and pharmacological interventions for preventing HF events among adults with stage 1 hypertension who also have an estimated 10-year atherosclerotic CVD risk of ≥10%, prevalent CVD, diabetes, or chronic kidney disease.
SPRINT (Systolic Blood Pressure Intervention Trial),
30 which is a major driver for the revisions in the 2017 ACC/AHA BP guideline, suggested that, among individuals at high risk for CVD events but without diabetes (baseline mean SBP/DBP 140/78 mm Hg), targeting SBP to <120 mm Hg instead of <140 mm Hg resulted in a 36% lower rate of acute decompensated HF.
31 Even so, it remains unclear how BP measurements in the SPRINT study collected in a highly controlled research setting correspond to BP measurements commonly obtained in a typical clinic setting. Furthermore, the SPRINT study included individuals at high risk for CVD events. Thus, it is unclear whether lowering the cutoff value of hypertension from 140/90 to 130/80 mm Hg would yield similar improvements in real-world clinical settings and among individuals with low CVD risk.
Given the relationship between stage 1 hypertension and a higher incidence of HF and AF in our study population, which included mainly subjects with relatively low CVD risk, an optimal management strategy is needed even among subjects with stage 1 hypertension and low CVD risk. For this reason, we need to consider the amount of time required to accumulate a sufficient number of HF and AF events among a sample population of adults with stage 1 hypertension with low CVD risk. Therefore, studies to evaluate left ventricular hypertrophy, which often precedes the development of HF and AF,
32 as a primary outcome would be an initial step toward providing evidence that pharmacological treatment is essential for subjects with elevated BP or stage 1 hypertension.
Strengths of this study include a large general population, the fact that participants were not taking antihypertensive medications at baseline, and high retention of participants. The JMDC data set includes medical and pharmacy claims data combined with annual health checkup data from employees’ health insurance programs in an anonymous format. Of note, clinical follow-up data obtained from claim records are also included in the JMDC database. Therefore, the JMDC database is theoretically capable of tracking all of an individual’s clinical information (such as diagnosis of HF and AF using ICD-10 codes) even if the patient sees different medical providers as long as the individual has the same insurance coverage.
This study has several limitations. BP measured at a single occasion was used for BP classification, which might not fully reflect a person’s BP phenotype. However, when we defined BP groups using the average of BP on 2 occasions (ie, at baseline and within the first year of follow-up), the association remained between stage 1 and stage 2 hypertension and a higher risk for HF and AF. The Japanese Ministry of Health, Labor, and Welfare requests health care professionals who engage in the Japanese health checkup system to follow the recommended protocol for BP measurements. However, in a real-world setting on a nationwide scale, adherence to the protocol might be limited. BP levels measured in routine clinical practice are generally higher than BP measurements in a highly controlled research setting, which might overestimate the true BP levels in routine clinical practice and underestimate the true associations between BP levels and CVD events.
33 In this health claims database, diseases were identified according to diagnostic codes. However, uncertainty remains about the accuracy of the diagnoses for HF, AF, MI, AP, and stroke. Of the records of 2 943 563 individuals collected between January 2005 and August 2018, we excluded 415 406 (14.1%) individuals missing data for BP and antihypertensive medication use, and characteristics of those included versus not included in the present study differed. The JMDC Claims Database included an employed, working-age population. Accordingly, mainly young and middle-aged adults were included in the present study, and the prevalence of diabetes was low.
34 Therefore, a “healthy worker” bias might be present in this population. Further investigation is needed to determine whether our results can be generalizable to other populations of different ethnicities, races, educational levels, and incomes. Detection bias may cause overestimation or underestimation of true correlation between high BP and HF/AF events. For example, AF was more likely to be diagnosed among the stage 1 and stage 2 hypertension group because those individuals use medical services more frequently compared with the normal BP group, which itself might influence the likelihood of disease detection. Possible residual confounding, including sodium intake and psychological factors, may affect the BP–CVD event associations.
35,36Conclusions
Stage 1 hypertension and stage 2 hypertension, as defined by the 2017 AHA/ACC BP guideline, were associated with higher risk of HF, AF, and other CVDs compared with normal BP in a large general population without known history of CVD. The ACC/AHA BP classification system may help identify adults at higher risk for HF and AF events.