It is well known that high blood pressure increases the risk of stroke - the fourth leading cause of death worldwide. The threshold for high blood pressure diagnosis, or hypertension, is 140/90 mmHg. But new research suggests that even people with blood pressure lower than this - but higher than normal - have an increased stroke risk.
For the study, the investigators analyzed all existing research that looked at the risk of stroke in people with prehypertension. This is when blood pressure is higher than normal (120/80 mmHg) but below the high blood pressure diagnosis threshold. The analysis included 19 studies involving more than 760,000 participants. All subjects were followed for between 4 and 36 years, and 25-54% of them had prehypertension.
The researchers found that individuals with prehypertension were 66% more likely to have a stroke than those who had normal blood pressure, and almost 20% of strokes that occurred in the study population were in those with prehypertension. These results remained even after the team adjusted for factors that may increase stroke risk, including smoking, diabetes and high cholesterol.
As part of the study, the researchers divided individuals with prehypertension into two groups. Participants in the "high" group had blood pressure over 130/85 mmHg, while those in the "low" group had blood pressure under this but above normal. This analysis revealed that participants in the high group were 95% more likely to have a stroke than those with normal blood pressure, while those in the low group were 44% more likely to have a stroke.
These findings, if confirmed, have important takeaways for the public. Considering the high proportion of the population who have higher than normal blood pressure, successful treatment of this condition could prevent many strokes and make a major difference in public health.