Age-Specific Relationship between Blood Pressure and the Risk of Total and Cardiovascular Mortality in Japanese Men and Women

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Abstract
To examine the impact of age on the relationship between blood pressure (BP) levels and each of cardiovascular disease mortality and all-cause mortality, a total of 30,226 men and 58,798 women aged 40-79 years who had no history of stroke or heart disease underwent health checkups in Ibaraki-ken, Japan, in 1993 and were followed through 2002. Risk ratios for mortality by BP category based on the 1999 WHO-ISH guidelines were calculated by age subgroups (40-59 years, 60-79 years) using a Cox proportional hazards model. Compared with optimal BP levels, the multivariate risk ratios of cardiovascular mortality for stage 2 or 3 hypertension were 5.99 (95% confidence interval: 2.13-16.8) in middle-aged men and 4.09 (1.70-9.85) in middle-aged women. These excess cardiovascular mortality risks were larger in the 40-59 years age group than in the 60-79 years age group for both genders (p for interaction = 0.01 for both). In men, the population attributable risk percents of cardiovascular mortality were 60% for younger men and 28% for older men, while for women they were 15% for younger women and 7% for older women. Weaker but significant excess risks of total mortality were observed for stage 2 or 3 hypertension in men of both age groups and in the older age group for women. The impact of BP on the risk of cardiovascular mortality was larger among middle-aged persons than among the elderly in both men and women. Our findings indicate the importance of BP control to prevent cardiovascular disease among middle-aged individuals.