More than 1.5 billion people will have high blood pressure by 2025, and the world's poorest countries will be worst hit, warn US experts.
High blood pressure is a risk factor for heart disease
Three-quarters will be from developing countries, Tulane University researchers estimate.
Unless treatments and prevention strategies are employed, millions will die from heart attacks and strokes in future years, they say in the Lancet.
They blame changes in diet and increasing levels of inactivity.
Until now, high blood pressure has largely been a disease of the more affluent countries.
Professor Jaing He and colleagues pooled data from 30 different studies involving more than 700,000 people from different regions of the world.
In 2000, about 972 million people had high blood pressure - a third in the developing world and two-thirds in western countries.
Based on trends, the researchers believe the prevalence of high blood pressure will increase by about 60% to 1.56 billion people by 2025.
The largest increase - 80% - will be in the developing world, with a smaller increase of 24% in developed countries, they predict.
Countries to be hit the hardest will include China and India, as well as regions of Latin America and the Caribbean, they say.
Professor He said: "High blood pressure is an important health issue not only because of its high frequency, but also because it is a major modifiable risk factor for cardiovascular disease.
"Cardiovascular diseases are now responsible for 30% of deaths worldwide."
He said there could be a worldwide epidemic of strokes and heart attacks in the future and that their 2025 projections are likely to be an underestimate of the true problem.
In the UK, about one in five people - at least 10 million - have high blood pressure.
Professor Peter Weissberg, medical director of the British Heart Foundation, said: "The authors have made a number of assumptions in coming to the figures for high blood pressure.
"Nevertheless, the overall message is alarming given that high blood pressure is a major risk factor for heart disease and is essentially avoidable.
"When coupled with the disturbing rise in obesity and type 2 diabetes, this study suggests that, unless effective public health measures are rapidly implemented, we will see a reversal of the current downward trend in death rates due to premature coronary heart disease and stroke.
"This paper shows the importance of public health measures to help people lose weight, increase their exercise levels, and decrease salt content in foods - all of which will lower blood pressure, and which the BHF support wholeheartedly.
"There is an even more important message for economically developing countries, to try not to go down the same lifestyle route as more developed countries have; a route which has led to huge heart health problems."