The study’s findings predict a huge burden of medical costs and physical disability ahead in this century, as the disease increases a person’s risk of heart attack, kidney failure, blindness and some infections.
“This study confirms the suspicion of many that diabetes has become a global epidemic,” said Frank Hu, an epidemiologist at Harvard’s School of Public Health who was not involved in the research. “It has the potential to overwhelm the health systems of many countries, especially developing countries.”
Worldwide, the prevalence of diabetes in men older than 25 rose from 8.3 percent in 1980 to 9.8 percent in 2008. For women older than 25, it increased from 7.5 percent to 9.2 percent.
“This is likely to be one of the defining features of global health in the coming decades,” said Majid Ezzati, an epidemiologist and biostatistician at Imperial College London, who headed the study. “There’s simply the magnitude of the problem. And then there’s the fact that unlike high blood pressure and high cholesterol, we don’t really have good treatments for diabetes.”
There are two types of diabetes, a metabolic ailment in which the body is unable to rapidly or adequately move sugar out of the bloodstream and into tissues after a meal. Type 1 is an autoimmune disease that comes on in childhood and requires that a person take insulin shots to survive. Type 2 accounts for 90 percent of cases and generally comes on after age 25. It is controlled by insulin, pills and, in some cases, weight loss and exercise.
The disease is most common in the islands of the South Pacific — Oceania — where an explosion of severe obesity, coupled with a genetic proclivity for diabetes, has driven diabetes prevalence to 25 percent in men and 32 percent in women in some places. The Gulf States also have very high rates, with Saudi Arabia ranking No. 3, Jordan No. 8 and Kuwait No. 10 in diabetes among men in 2008.
Among high-income countries, the United States had the steepest rise over the past three decades for men and the second-steepest rise for women (behind Spain). In 2008, 12.6 percent of American men and 9.1 percent of women had the disease.
China and India, however, are the nations that will be most responsible for what happens over the next several decades. Together, they account for 40 percent of people with diabetes today. In contrast, 10 percent of the world’s total live in the United States and Russia.
Barry M. Popkin, a professor of nutrition at the University of North Carolina who has done research in China, said the increase in diabetes there has just begun. That’s because diabetes lags behind inactivity and obesity, both of which have increased during China’s economic boom.
“In China, diabetes is essentially a problem of this decade. It’s a problem of the new millennium,” Popkin said. For that reason, he thinks the findings by Ezzati and his colleagues understate the problem.
“The rate of increase they found is very slow compared to what we are going to see in the next 20 years across the globe based on the current dynamics of diet, inactivity and obesity,” Popkin said. “You fast-forward and this scenario, which is scary enough, is going to be terrifying.”
India and its neighbors Pakistan and Bangladesh are unusual cases.
Over the past 30 years, men and women there have experienced little increase in obesity. However, those countries are among ones with the biggest rise in “fasting plasma glucose,” a blood sugar measurement taken before breakfast that best reflects diabetes risk.
People in this region probably have a genetic predisposition for diabetes. At any weight above normal, they are more likely to develop the disease than many other ethnic groups. Malnutrition during a woman’s pregnancy and in a child’s first years of life — problems that still exist in some parts of the region — also appear to increase a person’s chance of developing diabetes later in life.
Overall, though, “diabetes tracks very well with economic development and urbanization,” said Hu, the Harvard researcher. Much of Africa and some other big countries, such as Indonesia, are rapidly heading that way.
In the study, each country’s diabetes prevalence and average fasting blood sugar are “age-standardized” calculations. Each country is treated as if it had the same age structure of its adult population — the same number of people age 25 to 29, the same number 30 to 34, and so on. Age standardization allows researchers to compare countries whose populations have a high percentage of old people to nations with fewer old people.
The actual number of people in the world with diabetes, however, reflects not only the underlying rate of the disease in each age group but also the size and structure of the global population today.
Between 1980 and 2008, the number of diabetics more than doubled — from 153 million to 347 million. About 30 percent of that increase came from rising prevalence of the disease in all age groups. About 30 percent came from population growth, since more people means more diabetics. About 40 percent came from the aging of the world population; diabetes is more common in older people.
Is it a consolation that “demographic factors” such as population growth and aging explain most of the increase in the number of diabetics?
“Not if you are the minister of health,” Ezzati said, and “you still have to find a way to pay for the care of the number of diabetics there are in your country.”
Ezzati and his colleagues Goodarz Danaei and Mariel M. Finucane, both of Harvard, analyzed about 370 health surveys and epidemiological studies. Fasting blood sugar was lowest in sub-Saharan Africa, parts of Southeast Asia and Andean South America. Timor-Leste (which used to be part of Indonesia), Burma, Peru, Burundi and Cambodia were the bottom five countries for men’s blood sugar in 2008.