Trends for Blood Pressure and Its Contribution to Stroke Incidence in the Middle-Aged Japanese Population

Abstract

Background and Purpose-Hypertension is a major risk factor for stroke. However, a substantial decrease in blood pressure levels in Japanese during the past 3 decades may have reduced contributions of hypertension to risk of stroke. The population attributable fraction, the percentage of outcomes attributable to exposure, of blood pressure for the incidence of stroke was investigated during 3 survey periods between 1963 and 1994 by means of a population-based cohort study. Methods-We explored 3 cohort data of residents aged 40 to 69 years in 4 Japanese communities in 1963 to 1971 (nϭ5439), 1975 to 1984 (nϭ9945), and 1985 to 1994 (nϭ11 788) baseline surveys. Mean follow-up period for each cohort was 10 years. Results-Higher blood pressure levels were associated with higher risk of stroke. Positive associations were also observed even within nonhypertension levels. From the first to the third cohorts, the blood pressure category with a majority of stroke incidence shifted from severe or moderate hypertension to mild hypertension. The population attributable fraction of the severe hypertension category in the first, second, and third cohorts were 20%, 14%, and 9%, respectively, and those of the moderate hypertension category were 19%, 24%, and 11%, respectively, whereas those of the mild hypertension category were 17%, 26%, and 23%, respectively. The results were similar when participants on antihypertensive medication were excluded. Conclusions-The higher risk of stroke incidence with higher blood pressure levels even in nonhypertension categories and the shift of stroke burden from severe/moderate hypertension to mild hypertension support the early management of hypertension and primary prevention of high blood pressures for the prevention of stroke.

Lifetime risk of stroke and impact of hypertension: estimates from the adult health study in Hiroshima and Nagasaki

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“…The Circulatory Risk in Communities Study (CIRCS) is a prospective community-based study that has been launched to prevent stroke in five communities across Japan since 1963, described in detail elsewhere 6,13,14) . Annual cardiovascular risk surveys and monitoring of cardiovascular events are systematically conducted by a research team of the Osaka Medical Center for Health Science and Promotion, the Osaka University and the University of Tsukuba.…”

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