Nearly 10 per cent of the world's adults have diabetes, and the prevalence of the disease is rising rapidly. As in the United States and other wealthy nations, increased obesity and inactivity are the primary cause in developing countries such as India and in Latin America, the Caribbean and the Middle East.
That is the sobering conclusion of a study published Saturday in the medical journal The Lancet that traces trends in diabetes and average blood sugar readings in 200 countries and regions over the past three decades.
The study's findings predict a huge burden of medical costs and physical disability lying ahead in this century, as diabetes 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," 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 per cent in 1980 to 9.8 per cent in 2008. For women older than 25, it increased from 7.5 per cent to 9.2 per cent.
Majid Ezzati, an epidemiologist and biostatistician at Imperial College London, who headed the study, said: "This is likely to be one of the defining features of global health in the coming decades. 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, which is 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 occurs as an autoimmune disease that comes on in childhood and requires a person to take insulin shots to survive. Type 2 accounts for 90 per cent 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, where an explosion of severe obesity, coupled with a genetic proclivity for diabetes, has driven diabetes prevalence to 25 per cent in men and 32 per cent 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 per cent of American men and 9.1 per cent 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 per cent of people with diabetes today. In contrast, 10 per cent of the world's total live in the United States and Russia.
Barry 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 is 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," Mr Popkin said. For that reason, he thinks the findings by Dr 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," Mr Popkin said. "You fast-forward and this scenario, which is scary enough, is going to be terrifying."
India, and its neighbours Pakistan and Bangladesh, are unusual cases.
During 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 urbanisation," said Dr 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-standardised" calculations. Each country is treated as if it had the 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 standardisation allows researchers to compare countries whose populations have a high percentage of old people to countries ones 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 per cent of that increase came from rising prevalence of the disease in all age groups. About 30 per cent came from population growth, since more people means more diabetics. About 40 per cent came from the ageing of the world population; diabetes is more common in older people.