High blood pressure, once considered a scourge of wealthy nations, is now even more common in low- and middle-income countries, according to an analysis in the journal Circulation.
Globally, more than 30 percent of the population suffered from high blood pressure, otherwise known as hypertension, in 2010. That represents a notable increase over the span of a decade, driven by a dramatic rise of hypertension in less wealthy nations, according to the new study.
Elevated blood pressure, in turn, contributes to heart disease, stroke and chronic kidney disease. Public health officials call it the leading preventable cause of premature death worldwide. And 1.4 billion people worldwide now have that risk factor.
Researchers at Tulane University's School of Public Health and Tropical Medicine took the globe's blood pressure by searching through hundreds of individual studies published in recent years, focusing on people over the age of 20.
The studies incorporated data from 90 countries. Results from elsewhere were estimated based on data from similar countries.
Dr. Jiang He and his colleagues found that hypertension increased by nearly 8 percentage points between 2000 and 2010 in low- and middle-income countries, growing from 24 percent of the population to 32 percent. "Definitely it's an epidemic," He told Goats and Soda.
"Two things really surprised me" when the analysis was complete, He said. First, that hypertension had increased so rapidly in low- and middle-income nations, it is now a more common disease there than in wealthy nations.
As best as they can tell, in poor nations, 32 percent of people have high blood pressure, compared with 29 percent in high-income countries
"Traditionally we know that hypertension is associated with over-nutrition" and other features of high-income lifestyles, said He, who is a professor and department chair of epidemiology.
He suspects that the rapid increase in high blood pressure is due to the increasing urbanization in low- and middle-income countries. Urban diets are higher in sodium, fat and calories. "The urban environment is also high-stress, including work-related stress and low physical activity. All those contribute to hypertension," He said.
He's second surprise was that hypertension is rarely treated appropriately in low- and middle-income nations. His study found that fewer than 8 percent of people with the diagnosis had treatment that successfully lowered their blood pressure.
Effective drugs are available to treat high blood pressure, but people in low- and middle-income nations may not have access to health care or the funds to pay for these drugs, the article noted.
Because the study inferred hypertension rates from many countries rather than measuring them directly, the results (wordplay alert!) should be "taken with a grain of salt," Dr. Andrew Moran from Columbia University wrote in an editorial in Circulation.
Even so, he doesn't doubt that there has been a dramatic increase in high blood pressure in many parts of the world. "If you follow the other risk factors that are associated with it, like overweight and obesity, they track in a similar direction," Moran, a research scientist, told Goats and Soda. "That makes it believable."
The World Health Organization is striving to reduce noncommunicable diseases, including hypertension, by 25 percent by 2025. Unfortunately many trends are heading in the opposite direction at the moment, including hypertension rates.
"Drug treatment is not the first choice," He said. "The first choice is prevention."
"We'd all like to alleviate poverty and make healthy food more accessible to people and give people more healthy work environments," Moran said. But it's probably more realistic to focus on improving the diets of people in the rapidly urbanizing developing world by encouraging lower calorie intake as well as reducing salt in people's diets (though there are differing opinions about the role of salt in hypertension).
Psychological and social stress is also cited as a cause of high blood pressure (for example, this op-ed piece in The New York Times).
"We really have in the U.S. not spent enough time and effort looking at these underlying factors, social and psychological," Moran said. "I believe they are hugely important, but they're hard to measure and very hard to disentangle from alcohol, poor diet and high salt intake."
There's one glint of good news in the new study: It did document a modest decrease in hypertension in high-income countries. That suggests lifestyle changes can in fact reduce the rate of high blood pressure. Even so, Moran said some populations in the United States still see increases in high blood pressure, such as African-American men.