Long-term exposure to elevated blood pressure and mortality from cardiovascular disease in a Japanese population: the Ibaraki Prefectural Health Study

Abstract

High blood pressure (BP) has been well established as a leading risk factor for both cardiovascular disease and mortality in general. However, the effect of long-term exposure to elevated BP on mortality risks in Asian populations remains unclear. The purpose of this study was to investigate the effects of time-averaged BP levels over 5 years on subsequent cardiovascular disease mortalities in a Japanese population. A total of 46 484 adults (14 771 men and 31 713 women) aged 40-79 years, who had no history of stroke or heart disease and who underwent health checkups in Ibaraki prefecture, Japan, in 1993 and 1998 were followed up through 2005. Hazard ratios (HRs) for mortality were estimated using a Cox proportional hazard model. Multivariate HRs (95% confidence interval) associated with a 10 mm Hg increase in systolic BP were measured in 1993 and 1998, and their averages were 1.11 (1.05-1.16), 1.13 (1.07-1.18) and 1.17 (1.10-1.27), respectively. Multivariate HRs for a 10 mm Hg increase in time-averaged systolic BP were 1.12 (1.03-1.21) in men and 1.24 (1.13-1.35) in women. The subgroup analysis of antihypertensive use showed that multivariate HRs for time-averaged systolic BP were 1.20 (1.11-1.29) in sustained non-users and 1.17 (1.04-1.32) in sustained users. Similar results were also obtained for diastolic BP. In conclusion, long-term exposure to elevated BP substantially associates with excess risk for cardiovascular disease mortality among Japanese subjects, irrespective of antihypertensive medication use. Thus, appropriate management of BP is important in both users and non-users of antihypertensive medication. Keywords: antihypertensive medication use; cardiovascular disease; mortality; prospective cohort study; time-averaged blood pressure INTRODUCTION Elevated blood pressure (BP) is one of the major risk factors for mortality from cardiovascular disease (CVD) and all-cause comorbidity worldwide. [1][2][3][4] The excess risk for CVD and all-cause mortalities was substantially attributed to hypertension when compared with normal BP levels. 3 Therefore, management of hypertension is of utmost importance, not only in clinical practice but also in public health practice.Atherosclerotic vascular disease evolves slowly and is undoubtedly related to the cumulative exposure of individuals to CVD risk factors over a lifetime. 5 High BP is a typical example of such a lifelong exposure. Consequently, previous investigations analyzing the relationship of BP to CVD mortality risk might be limited by a failure to effectively characterize or adequately quantify long-term vascular exposure. Some previous investigations have highlighted the importance of BP levels over time on incidence risk for CVD. The

Long-Term Blood Pressure and Age-Related Macular Degeneration: The ALIENOR Study

“…However, except for smoking, epidemiological studies have reported conflicting results, particularly for BP, as some studies [13][14][15][16][17][18] found associations between higher risk of AMD and elevated blood pressure, while others did not. 7,8,10,[19][20][21][22][23] Studies that explored the impact of BP on cardiovascular diseases have demonstrated that long-term average BP is a better determinant of risk for cardiovascular disease events, 24,25 as the effect of high BP seems to be cumulative. By contrast, most of the studies focusing on the association of cardiovascular risk factors with AMD used a single time point for BP measurement (at baseline).…”

From casual blood pressure measurement to long-term blood pressure burden: better elucidation of the association between versatile blood pressures and cardiovascular events

“…We congratulate Sasai et al 2 for providing us the long-waited piece of the puzzle that time-averaged blood pressure has an important role in predicting cardiovascular mortality above casual blood pressure measurements in the Asian population. On the other hand, we have to point out that sizable residents excluded at first and second surveys, limited age inclusion criteria (40-79 years Figure 1 Three different statistical approaches to profile the long-term burden of the versatile blood pressure.…”

“…1 Despite a plethora of evidence showing that high blood pressure is closely related to the risk of cardiovascular disease, it is very intriguing that we are still not certain which location of blood pressure (radial, brachial or central), which component of blood pressure (systolic, diastolic or pulse) and which time period of blood pressure (daytime, nighttime or clinic) are most predictive and, therefore, clinically relevant. In this issue of the journal, Sasai et al 2 assessed the predictability of another important, and equally intriguing, aspect of high blood pressure, the long-term blood pressure burden, for cardiovascular and allcause mortality in 46 484 Japanese people free of prior cardiovascular diseases followed up for 7 years. They used averaged two blood pressure measurements taken 5 years apart as a proxy for long-term blood pressure burden.…”

“…To better profile the long-term burden of the versatile blood pressure, there are mainly three different statistical approaches developed (Figure 1). We will then briefly describe these three approaches and discuss the value of the study done by Sasai et al 2 under this context. First, it is traditionally assumed that every individual should have an underlying 'usual' blood pressure, which primarily accounts for all blood pressure-related vascular risk and for the benefits of antihypertensive drugs (the usual blood pressure hypothesis).…”

“…Surprisingly, the hazard ratio (for cardiovascular mortality) associated with averaged blood pressure is approximately 60% greater than that associated with baseline blood pressure in this Japanese population-based study, irrespective of the use of antihypertensive drugs. 2 The implications of this finding are (1) the 'regression dilution' effect of casual blood pressure on cardiovascular mortality does exist in the Japanese population, (2) the magnitude of the regression dilution effect (B60%) observed in the Japanese population is similar to that reported in Western populations 3,6 and (3) the magnitude of the 'regression to the mean' effect on blood pressure measurement might be similar between Japanese and Western populations although it was not assessed directly as the 'regression dilution' effect in this study. Taken together, the more pronounced predictability of averaged blood pressure shown in the Sasai's study further substantiates the prognostic significance of usual blood pressure in Asian populations.…”