THURSDAY, Nov. 6 (HealthDay News) -- Too many American adults are unaware of "pre-diabetes" and not enough take action to reduce their risk, according to a U.S. Centers for Disease Control and Prevention study released Thursday.

People with pre-diabetes -- a condition in which blood glucose levels are higher than normal but not high enough to be classified as diabetes -- are at increased risk for developing type 2 diabetes, heart disease and stroke. But lifestyle changes such as diet and exercise can prevent or delay development of diabetes and its complications.

More than 25 percent of Americans have pre-diabetes but, in 2006, only 4 percent of adults had ever been told they had the condition, said the CDC researchers, who analyzed data on about 24,000 adults who took part in the 2006 U.S. National Health Interview Survey.

There are five conditions indicative of pre-diabetes -- pre-diabetes itself, impaired fasting glucose, impaired glucose tolerance, borderline diabetes, and high blood sugar. Of the 984 people in the study who'd been told they had pre-diabetes, 64.4 percent were told they had borderline diabetes, 38.3 percent were told they had high blood sugar, 33.7 percent were told they had pre-diabetes itself, 15.5 percent were told they had impaired glucose tolerance, and 15. 2 percent were told they had impaired fasting glucose. In addition, 43.3 percent were told they had two or more of the five conditions.

Rates of pre-diabetes increased with age, ranging from 2.7 percent among those ages 18 to 44 to 6 percent among those over age 65. Rates also increased with weight -- 2.3 percent among those with normal weight, 3.9 percent among those who were overweight, and 6.3 percent among those who were obese.

The study also found that pre-diabetes was more common among women (4.8 percent) than men (3.2 percent), but found no significant race/ethnicity-related differences.

Of the 984 people who'd been told they had pre-diabetes, 68 percent tried to lose or control weight, 55 percent increased their levels of physical activity, and 60 percent reduced their intake of dietary fat or calories. Only 42 percent engaged in all three risk reduction activities, and 24 percent didn't participate in any of these activities, the study found.

The study was published in this week's issue of the Morbidity and Mortality Weekly Report, a CDC journal. It echoes a prior study, published in the same journal on Oct. 31, that found that the U.S. rate of new cases of full-blown type 2 diabetes has doubled over the past decade from 4.5 cases per 1,000 people in 1995-1997, to 9.1 cases per 1,000 people by 2007. The suspected cause: rising obesity rates.

It's not too late to turn those numbers around, experts said. "An important opportunity exists to reduce the preventable burden of diabetes and its complications by increasing awareness of pre-diabetes among those who have the condition, and encouraging the adoption of healthier lifestyles and risk reduction activities among all U.S. adults," the researchers wrote in a summary of their study.

They added that people at increased risk for diabetes should lose or control their weight, increase their physical activity levels, and be tested according to published recommendations.

More information

The U.S. National Diabetes Education Program has more about diabetes and pre-diabetes.