When it comes to high blood pressure it appears a little bit means a lot.  A new Chinese study finds anyone with a blood pressure even slightly above the optimal 120/80 may be at an increased risk for stroke.

"This concept of pre-hypertension or this slight elevation, I mean, it's really important. The study estimates that given the findings from their analysis that pre-hypertension is responsible for 20 percent of strokes -- that's really significant," said Dr. Irene Katzan, who did not take part in the study but treats stroke victims at Cleveland Clinic.

A blood pressure reading of 140/90 crosses the threshold into high blood pressure, so pre-hypertension is defined as a blood pressure between 120/80 and 140/90.

Researchers at Southern Medical University in Guangzhou, China analyzed 19 blood pressure studies involving more than 760,00 people. They were checking to see if high blood pressure alone increased someone's risk for a stroke, or if someone with even a slightly elevated blood pressure was also at risk.

They found people with pre-high blood pressure were 66 percent more likely to develop a stroke than people who had normal blood pressure. Researchers also determined that nearly 20 percent of strokes in the people they studied were caused by pre-hypertension.

Researchers say treating those with even a slightly elevated blood pressure could prevent many strokes. Katzan agrees.

"So, we know that high blood pressure, hypertension, is the most important modifiable risk factor for stroke," explained Katzan. "It's responsible for 30 percent of strokes. And now this study suggests that even a slight elevation in blood pressure is significant."

Complete finding for this study are available in the online journal Neurology.