LONDON/SAN DIEGO - The number of adults with diabetes worldwide has more than doubled since 1980 to 347 million, a far larger number than previously thought and one that suggests costs of treating the disease will also balloon.

In a study published in the The Lancet journal, an international team of researchers working with The World Health Organization found that rates of diabetes have either risen or at best remained the same in virtually all parts of the world in the past 30 years.

The estimated number of diabetics is markedly higher than a previous projections that put the number at 285 million worldwide. This study found that of the 347 million people with diabetes, 138 million live in China and India and another 36 million in the United States and Russia.

The most common type of diabetes, Type 2, is strongly associated with obesity and a sedentary lifestyle.

"Diabetes is becoming more common almost everywhere in the world," said Majid Ezzati, from Britain's Imperial College London, who led the study along with Goodarz Danaei from the Harvard School of Public Health in the United States.

"Unless we develop better programs for detecting people with elevated blood sugar and helping them to improve their diet and physical activity and control their weight, diabetes will inevitably continue to impose a major burden on health systems around the world," Danaei added in a joint statement.

People with diabetes have inadequate blood sugar control, which can lead to serious complications like heart disease and stroke, damage to the kidneys or nerves, and to blindness.

Experts say high blood glucose and diabetes cause around 3 million deaths globally each year, a number that will continue to rise as the number of people affected increases.

As a result, diabetes is a booming market for drugmakers like Novo Nordisk, Sanofi, Eli Lilly, Merck and Takeda.

Treatments avaliable

Dozens of diabetes treatments, both pills and injections, are on the market. Global sales of the medicines totaled $35 billion last year and could rise to as much as $48 billion by 2015, according to drug research firm IMS Health.

New research being presented this weekend at the annual meeting of the American Diabetes Association in San Diego will focus on experimental drugs and ways to combine classes of medicines to better control blood sugar.

"This is a chronic, progressive condition," said Dennis Urbaniak, vice president of Sanofi's diabetes division. "What we are most worried about is the number of people out there with diabetes that is not optimally controlled."

For the Lancet study, the largest of its kind for diabetes, researchers analyzed fasting plasma glucose (FPG) data from 2.7 million participants aged 25 and over across the world, and then used advanced statistical methods to estimate prevalence.

They found that between 1980 and 2008, the number of adults with the disease rose from 153 million to 347 million. Seventy percent of the rise was due to population growth and aging, with the other 30 percent due to higher prevalence, they said.

The proportion of adults with diabetes rose to 9.8 percent of men and 9.2 percent of women in 2008, compared with 8.3 percent of men and 7.5 percent of women in 1980.

Diabetes has taken off most dramatically in Pacific Island nations, which now have the highest diabetes levels in the world, the study found. In the Marshall Islands, a third of all women and a quarter of all men have diabetes.

Among wealthy countries, the rise in diabetes was highest in North America and relatively small in Western Europe. Diabetes and glucose levels were highest in United States, Greenland, Malta, New Zealand and Spain, and lowest in the Netherlands, Austria and France.

The region with the lowest glucose levels was sub-Saharan Africa, followed by east and southeast Asia.