Background and PurposeThis article examines prevalence of isolated systolic hypertension (ISH) in a population of Japanese-American men living in Hawaii and compares rates of stroke among those with ISH, isolated diastolic hypertension (IDH), combined systolic/diastolic hypertension (SDH), and nonhypertension.MethodsEight thousand six men aged 45 to 68 years participated in a baseline examination as part of a prospective study of coronary heart disease and stroke and were followed up for 20 years for incident disease and total mortality. Men were divided into four groups according to baseline blood pressure: ISH (systolic blood pressure [SBP] greater than or equal to 160 mm Hg and diastolic blood pressure [DBP] less than 90 mm Hg); IDH (SBP < 160 mm Hg and DBP greater than or equal to 90 mm Hg); SDH (SBP greater than or equal to 160 mm Hg and DBP greater than or equal to 90 mm Hg); and nonhypertension (SBP < 160 mm Hg and DBP < 90 mm Hg).ResultsMen with ISH had the highest rates of stroke, followed by men with SDH. Men with IDH had rates only slightly higher than men in the nonhypertension group. Relative risk adjusted for other risk factors varied by age group. For men aged 45 to 54 years, relative risks of stroke associated with ISH, IDH, and SDH compared with nonhypertensive subjects were 4.8, 1.4, and 4.3, respectively. For men aged 55 to 68 years, the same relative risks were 1.2, 1.8, and 1.7. Excluding men on antihypertensive medication at baseline did not alter results.ConclusionsISH had a much greater impact on risk of stroke in younger than in older men. The results suggest that while ISH is more common in older men, in younger men it is associated with higher relative risk of stroke.(Stroke. 1995;26:25-29.)