Currently, elevated blood pressure (hypertension) is a known risk factor for stroke. The positive effect of eliminating hypertension on stroke occurrence is apparent within a few years of blood pressure control. The effect of hypertension in the distant past on stroke risk is less clear. The recognition of the complications of long-term hypertension, such as left ventricular hypertrophy and carotid stenosis, as risk factors for stroke imply that more distant antecedent hypertension may also increase stroke risk. Seshadri and associates used prospectively collected, population-based data from the Framingham Study to look at the importance of past blood pressure in determining stroke risk in older men and women (60 years and older) after controlling for current blood pressure.
There were 830 completed ischemic strokes during the 50-year follow-up of the 5,197 subjects. Of these stroke episodes, 491 occurred in the 3,761 subjects who had a blood pressure measurement at their last baseline (age 60, 70, or 80 years) and had information about smoking and diabetes status. Higher current blood pressure at any of the baselines was clearly associated with increased 10-year risk of stroke, which was highest at age 60 years. After adjusting for the current blood pressure, earlier antecedent blood pressure elevation further increased stroke risk. This effect was present in men and women.
The authors concluded that antecedent blood pressure increases future stroke risk. With this evidence that midlife blood pressure affects stroke risk over a long period of time—up to 30 years—emphasis should be on more of an effort to reduce blood pressure earlier in adult patients.