More than 50 million Americans live with a disability, health officials reported Thursday.

The most common disabilities are mobility limitations, such as having serious difficulty walking or climbing stairs -- affecting one in eight adults -- followed by disabilities in thinking and/or memory, independent living, seeing and self-care, according to a new report from the U.S. Centers for Disease Control and Prevention.

"This report is a snapshot of the percent of adults with disabilities in the U.S., so we can get a better understanding of who people with disabilities are," said researcher Elizabeth Courtney-Long, a health scientist at the CDC's National Center on Birth Defects and Developmental Disabilities.

The researchers found that most people with disabilities live in southern states, such as Alabama (31.5 percent), Mississippi and Tennessee (31.4 percent).

Although why these states tend to have the highest number of disabled people isn't known, the researchers suggested that states in the South have higher rates of chronic diseases, such as heart disease and diabetes, which may be linked to disability.

People with disabilities were also more likely to be aged 65 and older, Courtney-Long said.

In addition, the researchers found blacks (29 percent) and Hispanics (26 percent) were more likely to suffer from disabilities than whites (nearly 21 percent).

Moreover, education and income levels appear to have strong ties to disability rates.

Nearly 40 percent of people in the study who had less than a high school education reported a disability.

Also, about 47 percent of people who had annual household incomes of less than $15,000, and about one-third of unemployed people who were able to work reported a disability, the study found.

According to the report, more women than men have a disability (more than 24 percent versus nearly 20 percent, respectively).

Costs for maintaining health among people with disabilities were estimated at nearly $400 billion in 2006, the researchers reported. More than half of these costs were related to non-independent living, such as institutional care and personal-care services.

The findings were published July 31 in the CDC's Morbidity and Mortality Weekly Report.

"We are all at risk of having a disability at some point in our lifetime," CDC Director Dr. Tom Frieden said in a CDC statement. "Health professionals and health care systems need to meet the needs of this growing population," he added.

Dr. David Katz, director of the Yale University Prevention Research Center in New Haven, Conn., said that much of the disabilities and chronic disease people suffer from can be eliminated.

"Life expectancy is rising in the United States, which can convey a false sense of security about our health," Katz said.

The National Academy of Medicine has issued reports showing that health and vitality are not keeping pace with longevity, and that the gap between the two is potentially widening, he said.

"Although medical advances help delay death, they cannot confer genuine vitality," Katz said. "The consequence of a longer life span, but a health span that is not keeping pace, is more years encumbered by chronic maladies and disabilities," he said. "Much of this is preventable."

By eating well, being active and not smoking, as much as 80 percent of chronic diseases could be prevented, as well as the disability that accompanies them, Katz said.

"The true prize is a combination of more years in life, and more life in years -- and the best medicine for producing that outcome is not at the cutting edge of biomedical advance -- it is lifestyle," he said.

All disability cannot be prevented, Katz said. "But much of the disability we encounter in our culture is indeed a byproduct of choices we make both individually and collectively, choices that we can alter," he said.