A government survey released in 2009 finds that 48 million American adults, about 1 in 5, are living with a disability and that the most common cause of disability is arthritis.

The report, which was released by the Centers for Disease Control and Prevention in Atlanta, is the first survey of disability in the United States in a decade. It shows that the level of Americans reporting a disability has remained nearly unchanged since 1999, when by the same definitions, 22 percent of Americans reported being disabled.

But researchers cautioned that the absolute number of disabled people has increased by 3.4 million since 1999, and that it would continue to rise as the baby boom generation ages.

“With the aging of the baby boomers, the prevalence of arthritis is expected to rise by 40 percent – that is up to 67 million people – by the year 2030,” said Jack Klippel, MD, president and chief executive officer of the Arthritis Foundation, in a press statement.  “These findings suggest a critical need to expand the reach of effective strategies aimed a disability prevention and management,” he said.

In the 2009 study, about 9 million people report being disabled by arthritis. The second most common cause, affecting 7.5 million, was back problems, followed by heart trouble (roughly 3 milllion), lung or respiratory problems and mental or emotional problems (about 2.2 million each).

More women report being disabled than men, and the risk of disability rises with age, affecting a greater proportion of people over the age of 65 than any other group. 

In absolute numbers, however, nearly as many baby boomers, who range in age from 45 to 65, reported disabilities, roughly 17.3 million, as did adults over the age of 65, 18.1 million.

Among people reporting a disability, 22.5 million reported that it was difficult to walk three blocks; 21.7 million said it was hard to climb a flight of stairs; and 13.5 million were challenged by activities of daily living, such as housework and meal preparation.