The number of Americans with diabetes increased by 15 percent in two years to nearly 24 million, public health officials reported yesterday.

Almost 8 percent of the total population now has the disease, which is linked to obesity and sedentary living, according to the U.S. Centers for Disease Control and Prevention.

The latest numbers are estimates for 2007 and include people who have been diagnosed with diabetes as well as those who likely have it but don't know it, the agency said.

The estimated number of people with undiagnosed diabetes actually went down, to 5.7 million in 2007 from 6.2 million in 2005, indicating an increase an awareness about the disease, the CDC said.

But an increase in diagnosed cases more than made up the difference. And the CDC warned that another 57 million people were estimated to have pre-diabetes, a condition that put them at increased risk for the disease.

Prevalence varied dramatically by age, race and ethnicity, as it has in the past. Nearly 25 percent of Americans age 60 and older had either diagnosed or undiagnosed diabetes in 2007, the CDC said.

When the agency adjusted for population age differences among different groups in the United States, it found diabetes rates among American Indians and Alaska natives of 16.5 percent; blacks, 11.8 percent; Hispanics, 10.4 percent; Asians, 7.5 percent, and whites, 6.6 percent.

Diabetes is the seventh-leading cause of death in the U.S. and can lead to heart disease, blindness, kidney failure and amputation, according to the National Institutes of Health. Two-thirds of diabetics eventually die from heart attack or stroke, many of them unaware of their heightened risks.

Worldwide, the number of people with diabetes is expected to double to 366 million by 2030, according to the World Health Organization.