A new study has found that the number of U.S. adults diagnosed with diabetes has nearly tripled in the past three decades to 24.7 million people. Worldwide, the incidence of diabetes has doubled compared with the rate 30 years ago, to 347 million cases, according to the study, which was recently published in the British medical journal The Lancet.

Nearly 162,000 Iowans, or about 7 percent of adults in the state, have been diagnosed with diabetes, a 40 percent increase in just the past decade, according to the latest figures from the Iowa Department of Public Health (IDPH) in 2009. The IDPH also estimates that as many as 30 percent of Iowa adults may have undiagnosed diabetes or prediabetes, a figure that mirrors national trends.

The total cost of treating diagnosed diabetes cases in the United States was estimated at $174 billion in 2007.

Health officials attribute much of the increase in type 2 diabetes, a chronic disorder marked by high blood-sugar levels, to poor diet, lack of exercise and obesity. If current trends continue, as many as one out of every three adults in the United States could have the disease by 2050, say experts at the U.S. Centers for Disease Control and Prevention. If left untreated, diabetes can lead to a long list of health complications, such as heart disease and stroke, kidney disease, high blood pressure, blindness, nerve problems and amputations.

The American Diabetes Association recommends that those 45 years or older should be tested for diabetes every three years, particularly if they are overweight or have one or more risk factors, including a family history of diabetes, lack of regular exercise or high blood pressure.