A government report found that the number of American adults with arthritis is rising, and along with it, so is the disabling impact of the disease.

The 2010 report from the Centers for Disease Control and Prevention (CDC) shows that the number of people older than age 18 with doctor-diagnosed arthritis has climbed from roughly 46 million to 50 million over the last four years.

That increase is in line with previous predictions that cases of arthritis would rise with the aging of the population.

The report, containing data from 2007 through 2009, says 22 percent of the population has arthritis, which costs our economy $128 billion a year.

What has experts most concerned, however, is the sharp increase in the percentage of people with arthritis who say that they have to skip some everyday activities – things like climbing stairs, grocery shopping or jogging – because of their disease, which can cause severe pain and limited mobility.

“The one thing we know is arthritis prevalence is growing at about one million people a year, but the surprising finding was the number of adults with activity limitation is growing faster than we expected,” says Jennifer Hootman, PhD, an epidemiologist with the CDC’s Arthritis Program.

Some 21 million adults, or nearly 1 in 10, say arthritis limits their daily activities.

That’s two million more than the CDC had previously estimated and not far off from the projection of 25 million that wasn’t expected until 2030.

“We’ve still got a long time to go before 2030 and we’re almost there [to the 25 million mark],” Dr. Hootman says. “It’s growing at a much faster pace than we had projected.”

Activity limitation is defined as any kind of regular activity that someone wants to do but can’t because of arthritis and its symptoms.

“I think people haven’t understood what arthritis being the most common cause of disability means. It means that people lose independence and that is a powerful thing and I think we are looking at it starkly when we see that people are having activity limitations,” says Patience White, MD, vice president for public health at the Arthritis Foundation and professor of medicine and pediatrics at George Washington University School of Medicine in Washington, D.C.