FRIDAY, Jan. 4 (HealthDay News) -- Arthritic disease is the most common cause of disability in the United States and now affects 46 million Americans, or more than 21 percent of the adult population, a major new report finds.

That number is expected to rise even higher as baby boomers age, so that by 2030, 40 percent of American adults will suffer from some form of arthritic disease, the researchers said.

Today, almost two-thirds of people with arthritis are under 65, and more than 60 percent are women. The disease hits whites and blacks equally, but the rate is lower among Hispanics, according to the report.

"Arthritis remains a large and growing problem," said lead researcher Dr. Charles G. Helmick, an epidemiologist with the U.S. Centers for Disease Control and Prevention. "Cases of osteoarthritis has risen, while rheumatoid arthritis has gone down since our last estimate," he added.

Rheumatoid arthritis is a painful autoimmune disorder of uncertain origin leading to chronic inflammation at the joints. Osteoarthritis is a more common illness caused by a gradual breakdown of cartilage in the joints.

The reasons why there are now fewer cases of rheumatoid arthritis is unclear, Helmick said. One reason may be that experts have changed the way they estimate the number of cases. Today, they use a more specific and restrictive definition of the condition, he said. But there has been a real decreases in cases of rheumatoid arthritis worldwide, and no one is sure why, Helmick added.

The main reason that osteoarthritis is increasing is an aging population, Helmick said. "As more people age, there will be more people with osteoarthritis. That's what's driving the numbers upward," he said.

Also, the obesity epidemic in the Unites States is taking its toll, Helmick noted. "Obesity is a risk factor for knee osteoarthritis, one of the most common types of arthritis," Helmick said. "We don't have any cures, we treat the symptoms and, when it gets bad enough, we do knee replacements, which are very expensive," he said.

As more people suffer from arthritis, the costs associated with the disease will also keep going up. Currently, the costs to the country from arthritis top more than $128 billion a year in lost earnings and medical care, Helmick said.

The researchers, from the National Arthritis Data Workgroup, used data from the U.S. Census Bureau, national surveys, and findings from community-based studies across the United States to determine the prevalence of arthritis in 2005 and beyond. The results were published in two papers in the January issue of Arthritis & Rheumatism.

Key findings in the report include:

• By 2030, almost 67 million people will have arthritis -- an increase of 40 percent. Osteoarthritis, the most common type of arthritis, affects almost 27 million Americans. That's a big increase from 1990, when 21 million suffered from the condition.
• The prevalence of rheumatoid arthritis has declined to 1.3 million Americans, from 2.1 million in 1990.
• The prevalence of gout, a form of inflammatory arthritis, has risen in 2005 to about 3 million up, from 2.1 million in 1990.
• Currently, juvenile arthritis affects some 294,000 children between infancy and age 17.
• An estimated 59 million Americans have suffered an episode of low back pain over the past three months, the researchers said, while 30 million have suffered neck pain over the same time period.

In addition, the report includes estimates for related conditions such as fibromyalgia, spondylarthritides, systemic lupus erythematosus (lupus), systemic sclerosis, Sjgren's syndrome, carpal tunnel syndrome, polymyalgia, and rheumatic/giant cell arteritis.

One expert advised staying active and keeping your weight under control to help prevent or treat arthritis.

"We know that cases of osteoarthritis are likely to grow, because it's age-related," said Dr. Patience White, chief public health officer at the Arthritis Foundation. "In addition, weight plays a big role in risk, as well as lack of physical activity, in keeping your muscles strong," she said.

Losing weight and keeping physically active can help to reduce pain and keep the disease at bay, White said. "If you lose as little as 10 pounds, you can decrease pain in the knees and hips by 50 percent," she said. "With exercise, you can decrease progression."

More information

For more information on arthritis, visit the Arthritis Foundation.

SOURCES: Charles G. Helmick, M.D., epidemiologist, U.S. Centers for Disease Control and Prevention, Atlanta; Patience White, M.D., Chief Public Health Officer, Arthritis Foundation, Atlanta; January 2008, Arthritis & Rheumatism

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