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Influence of systolic and diastolic blood pressure on stroke risk: a prospective observational study
E Lindenstrøm1, G Boysen, J Nyboe
1Hvidovre Hospital, Department of Neurology, Denmark.
Insights
Systolic blood pressure (SBP) is a stronger predictor of stroke risk than diastolic blood pressure (DBP). Higher SBP levels significantly increase stroke risk, particularly in the upper 40% of the population distribution.
Area of Science:
- Cardiovascular epidemiology
- Public health research
- Clinical hypertension
Background:
- Elevated blood pressure is a major risk factor for stroke.
- Understanding the differential impact of systolic and diastolic blood pressure on stroke risk is crucial for effective prevention strategies.
Purpose of the Study:
- To investigate the independent and combined effects of systolic blood pressure (SBP) and diastolic blood pressure (DBP) on the risk of stroke.
- To determine whether the relationship between blood pressure and stroke risk is log-linear.
Main Methods:
- Prospective cohort study (Copenhagen City Heart Study) of 19,698 participants.
- Two cardiovascular examinations with blood pressure measurements at 5-year intervals.
- Cox regression analysis to assess stroke risk associated with SBP and DBP, considering antihypertensive treatment.
Main Results:
- Both SBP and DBP showed significant associations with stroke risk when analyzed separately.
- When analyzed together, SBP remained a significant predictor, while DBP's effect diminished.
- Individuals on antihypertensive treatment had a 1.6 times higher stroke risk compared to untreated individuals with similar blood pressure.
- The highest SBP levels were associated with a 4.0-fold increased stroke risk.
- Attributable risk for SBP in the upper 40% was 22%.
Conclusions:
- The association between blood pressure and stroke risk is not log-linear.
- Systolic blood pressure is a more potent predictor of stroke risk than diastolic blood pressure.
- Public health efforts should focus on managing SBP for stroke prevention.
Abstract:
The purpose of this study was to estimate the influence of systolic (SBP) and diastolic blood pressure (DBP) on stroke risk. The Copenhagen City Heart Study is a prospective survey of 19,698 women and men who were invited to two cardiovascular examinations at 5-year intervals. Blood pressure was measured in participants once at each examination, together with other variables. Initial cases of stroke and transient ischemic attack were recorded from hospital records and death certificates from 1976 through 1988. When entered separately in the Cox regression model, both SBP and DBP had significant effects on stroke risk. In the lower 60% of the blood pressure distribution in the population, the relative risk of stroke was nearly constant, followed by a gradual increase in the upper 40% of blood pressure distribution. However, when SBP and DBP were entered simultaneously in the model, the effect of DBP vanished, while the pattern of the association between SBP and stroke risk remained unchanged. Persons on antihypertensive treatment had higher risk for stroke than non-treated persons with the same blood pressure, relative risk = 1.6 (95% confidence interval (CI) 1.2-2.2). The relative risk for the highest SBP levels, shared by nearly 3% of the population, was 4.0 (95% CI 2.2-7.3). The attributable risk of SBP in the upper 40% of SBP distribution, i.e., above the mean for each age and sex group, was 22%. Our results indicate that: 1) the association between blood pressure and stroke risk was not log-linear, and 2) SBP was a stronger stroke predictor than DBP.