The whole world is getting fatter, except perhaps for the women of Italy and Singapore. Globally, blood pressure is slowly coming down. Cholesterol is falling in rich countries and rising in developing ones.
Those three variables are sketching a complicated and constantly changing picture of the world’s risk for cardiovascular disease, which now kills more people than any other cause of death.
A massive project published Thursday is giving researchers and governments the clearest picture yet of trends of cardiac risk factors over the past generation, and hints at what may lie ahead.
“Our results show that overweight and obesity, high blood pressure and high cholesterol are no longer Western problems or problems of wealthy nations,” said Majid Ezzati, the epidemiologist at Imperial College London who headed the project. “Their presence has shifted towards low- and middle-income countries, making them global problems.”
Ezzati and more than a 100 collaborators used national data and surveys from 199 countries and regions to produce an epidemiological mosaic that reveals a big picture as well as telling details. The latter includes the heaviest group of people on Earth (men and women on the Pacific island of Nauru), the people with the lowest blood pressure (South Korean women), and those with the worst cholesterol (Icelandic men and women in Greenland).
The findings, published in three papers in the Lancet, also document considerable progress in recent decades, especially in the industrialized nations.
For example, the United States and Australia now have some of the lowest average blood pressures in the world. The United States, Canada, Sweden and Finland have also achieved large drops in average cholesterol in their populations in the past 20 years. At the same time, some of those places have seen steep increases in weight, as measured by body mass index, or BMI.
Ezzati hopes the information will be used to better understand which public health interventions have worked in recent decades.
“This effort is amazing, and the findings are very, very interesting,” said Christopher Murray, a physician and biostatistician who heads the University of Washington’s Institute for Health Metrics and Evaluation, as well as a former colleague of Ezzati’s at Harvard University.
“Once you have something like this, you can shift the conversation to an entirely new level,” Murray said. “You can start having a discussion of why countries have been more or less successful changing these risks, and that’s a hugely important conversation.”
Body weight, blood pressure and cholesterol are products of culture, diet and genetics. They raise the risk for heart attack and stroke independently, and to a lesser extent by affecting one another. For example, gaining weight often raises a person’s blood pressure. It may also increase blood cholesterol, depending on whether the increased calories come from fat or other food sources.
Two other important risk factors – smoking and blood sugar – were not included in the analysis. A study of rising blood sugar and rates of diabetes worldwide is under way, Ezzati said.
From 1980 to 2008, the average BMI for men rose in all but eight countries and for women in all but 19. Obesity, defined as a BMI over 35 kilograms per square meter of body surface, increased from 4.8 percent of the world’s men in 1980 to 9.8 percent now. For women, it rose from 7.9 percent to 13.8 percent.
“This is one of the great pandemics of the 21st century. Its consequences are huge,” said Richard Feachem, a professor of global health at the University of California at San Francisco who was not involved in the project.
North American men have an average BMI of 28.4 (about 197 pounds for a 5-foot-10-inch man). Women in North America, northern Africa, southern Africa and the Middle East all have average BMIs over 28 (163 pounds for a 5-foot-4-inch woman). In contrast, Japanese women have an average BMI of 21.9 (127 pounds for a 5-4 woman), and many other East Asian women are nearly as slim.
In the world’s two most populous nations, China and India, BMI for both sexes is lower than the global average, although for Chinese men it’s rising fast.
Blood pressure has generally improved. Normal blood pressure is typically defined as 120/80 millimeters of mercury, with the top (or systolic) number more important in determining risk of heart attack or stroke. Worldwide, that number declined from 131 to 128 for men, and from 127 to 124 for women, since 1980.
Treatment of hypertension and efforts to limit salt in the diet have produced huge reductions in blood pressure in the United States. Today, American men have the lowest blood pressure (123 systolic), and women the fourth-lowest (117 systolic), among residents of industrialized countries. In contrast, blood pressure is highest in the Baltic countries, and in east and west Africa, where it’s 138 for men and 135 for women.
Worldwide, cholesterol levels changed little over the past three decades. For men, it is 179 milligrams per deciliter, and for women, 184. (The target for healthful cholesterol is below 200).
That stability, however, masks some big winners and losers, and important trends.
Finland is a hotbed of heart disease. It may now qualify for the “most improved” prize in reducing its cardiac risk factors. For men, cholesterol fell from 244 to 201 between 1980 and 2008, and its systolic blood pressure declined from 143 to 135.
Elsewhere, in Europe, North America and Australia, cholesterol levels also fell, a consequence of the use of cholesterol-lowering drugs and some dietary changes. In East and Southeast Asia, cholesterol rose, probably from additional animal fat in the diet that came with greater wealth.
“We are seeing a convergence of Western countries and Asian countries,” Ezzati said.
A major question is whether Asian countries with rising cholesterol and blood pressure will experience an epidemic of heart disease, as occurred in Western countries in the post-World War II decades, or avoid that fate through behavior change, aggressive medical treatment and public health campaigns.
“The lessons of history are not encouraging,” Feachem said, noting that in most countries smoking must rise to high levels and cause major health effects before it’s addressed as a public health problem. With these other risk factors “we would hope that wouldn’t be the case, but it has a history of being so.”