That number has more than doubled in three decades, jumping to an estimated 347 million, a new study says. And with the numbers climbing almost everywhere, experts said the disease is no longer limited to rich countries and is now a global problem.

“Diabetes may well become the defining issue of global health for the next decade,” said Majid Ezzati, chair of global environmental health at Imperial College London, one of the study authors.

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.

And Ezzati noted the figures don’t even reflect the generations of overweight children and young adults who have yet to reach middle age. That could create a massive burden on health systems.

“We are not at the peak of this wave yet,” he said. “And unlike high blood pressure and cholesterol, we still don’t have great treatments for diabetes.”

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’s another sobering conclusion of the study, published Saturday in the journal Lancet, that traces trends in diabetes and average blood sugar readings in about 200 countries and regions over the past three decades.

“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.”