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.