New cases of type 2 diabetes are rising dramatically among U.S. adults, a new study shows.

The study appears in the journal Circulation’s rapid access online edition. It tracks new cases of type 2 diabetes in about 3,100 men and women from the 1970s through the 1990s.

The key finding? New cases (incidence) of diabetes doubled during the last 30 years, mainly among obese people, write Caroline Fox, MD, MPH, and colleagues.

Fox works with the National Heart, Lung, and Blood Institute’s Framingham Heart Study, a long-term heart study based in Framingham, Mass. The new diabetes data comes from the adult children of Framingham Heart Study participants.

Diabetes Continues Rapid Rise

New Cases More Common

When the study started, none of the participants had diabetes. At least once a decade, the men and women got checkups for the study. Those checkups included three measurements: height, weight, and blood sugar levels after fasting.

The study included 1,587 women and 1,517 men, divided into three cohorts of similar age. At the start in each decade, participants in the group to be studied were about 47 years old.

In the group studied during the 1970s, type 2 diabetes was diagnosed in 2 percent of the women and 2.7 percent of the men. In the 1980s group, those figures rose to 3 percent for women and 3.6 percent for men. During the 1990s, the numbers were their highest in 30 years: 3.7 percent for women and 5.8 percent for men in that group.

Type 2 diabetes is more common than type 1 diabetes. In both types of diabetes, the body has trouble controlling blood sugar due to problems with insulin, a hormone that controls blood sugar.

In type 1 diabetes, the body loses its ability to make insulin. In type 2 diabetes, the body can still make insulin, but doesn’t heed insulin like it should. As a result, the body has to ramp up insulin production and loses its ability to keep pace with demand, leading to high levels of blood sugar.

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Obesity Link

Most of the new cases in the study stemmed from obesity, defined as BMI (body mass index) of 30 or above.

“The cause of the increase in diabetes incidence is likely related to changes in obesity and lifestyle,” write Fox and colleagues. “Obesity and weight gain are the leading risk factors for the development of diabetes.”

Average BMI rose for both men and women during the study. But BMI doesn’t totally explain the increase in new cases of type 2 diabetes, the researchers note.

Growing waists might carry the greatest diabetes risk, but BMI doesn’t show where extra pounds are located, the researchers note. Fox’s team didn’t have data on waist size during the study’s early years.

The researchers also didn’t have details on participants’ physical activity and diet.

Most Framingham participants were white. It’s not known if the findings apply to other groups.

Diabetes FAQ

Diabetes Symptoms

Diabetes, which raises the risk of heart disease or stroke, often goes undiagnosed. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) lists these warning symptoms:

Being very thirsty Urinating often Feeling very hungry or tired Losing weight without trying Having sores that heal slowly Having dry, itchy skin Losing the feeling in your feet or having tingling in your feet Having blurry eyesight

Those symptoms don’t automatically mean someone has diabetes. If you’re concerned, see a doctor for a diabetes evaluation.

By Miranda Hitti, reviewed by Louise Chang, MD

SOURCES: Fox, C. Circulation, June 20, 2006; rapid access online edition. National Diabetes Information Clearinghouse of the National Institute of Diabetes and Digestive and Kidney Diseases: “What Diabetes Is.” News release, American Heart Association.