INFLUENCE OF SYSTOLIC AND DIASTOLIC BLOOD-PRESSURE ON STROKE RISK - APROSPECTIVE OBSERVATIONAL STUDY

The purpose of this study was to estimate the influence of systolic (S EP) and diastolic blood pressure (DBP) on stroke risk, The Copenhagen City Heart Study is a prospective survey of 19,698 women and men who w ere invited to two cardiovascular examinations at 5-year intervals, Bl ood pressure was measured in participants once at each examination, to gether with other variables. initial cases of stroke and transient isc hemic attack were recorded from hospital records and death certificate s from 1976 through 1988. When entered separately in the Cox regressio n model, both SEP and DBP had significant effects on stroke risk. In t he lower 60% of the blood pressure distribution in the population, the relative risk of stroke was nearly constant, followed by a gradual in crease in the upper 40% of blood pressure distribution. However, when SEP and DBP were entered simultaneously in the model, the effect of DB P vanished, while the pattern of the association between SEP and strok e risk remained unchanged. Persons on antihypertensive treatment had h igher risk for stroke than non-treated persons with the same blood pre ssure, relative risk = 1.6 (95% confidence interval (CI) 1.2-2.2). The relative risk for the highest SEP levels, shared by nearly 3% of the population, was 4.0 (95% CI 2.2-7.3). The attributable risk of SEP in the upper 40% of SEP distribution, i.e., above the mean for each age a nd sex group, was 22%. Our results indicate that: 1) the association b etween blood pressure and stroke risk was not log-linear, and 2) SEP w as a stronger stroke predictor than DBP.