A meta-analysis published in Neurology found that patients with a BP over 120/80mmHg but below 140/90mmHg, known as pre-hypertension, had a 66% greater risk of stroke compared with patients with normal BP of 120/80mmHg.
Risk rose sharply as BP increased, researchers saw. While patients between 120/80 and 130/85mmHg had a 44% higher risk of stroke, those with BP over 130/85 had a 95% greater risk.
The research, which examined over 760,000 participants across 19 studies, suggests nearly 20% of strokes in these patients were caused by pre-hypertension.
Study author Dingli Xu of the Southern Medical University in Guangzhou, China, said: 'Considering the high proportion of the population who have higher than normal BP, successful treatment of this condition could prevent many strokes and make a major difference in public health.'