Workers with rheumatoid arthritis have higher health care and other costs for U.S. employers than workers without the condition, a new study finds.

Rheumatoid arthritis is an autoimmune disease that causes pain, swelling, stiffness and loss of function in the joints, and can also affect other body organs.

The study appears in the March issue of the Journal of Occupational and Environmental Medicine.

Researchers analyzed an insurance-claims database to compare the costs to employers for more than 2,700 workers with rheumatoid arthritis and more than 338,000 workers without the condition. Their study included direct health care costs and indirect costs such as missed work days.

The study found that the average yearly cost for a worker with rheumatoid arthritis was $8,700, compared with $3,500 for a worker without the condition. Direct health care costs accounted for 90 percent of the extra $5,200 in the total yearly costs for a worker with arthritis, according to a journal news release.

The researchers also found that workers with rheumatoid arthritis averaged about three and a half more days of health-related work absences a year than those without arthritis. This included more sick days and more short-term disability time.

Based on their findings, the researchers calculated that workers with rheumatoid arthritis cost employers nationwide an additional $5.8 billion a year, compared to workers without it. Of that total, $5.2 billion is for direct health care costs. Workers with the condition also account for 4 million more lost work days per year than those without rheumatoid arthritis.

The study may underestimate the cost impact of rheumatoid arthritis for employers, particularly in reduced productivity, the researchers said.

"The data emphasize the need for effective management strategies that can reduce the burden of illness and economic losses incurred," concluded study co-author Richard Brook, of the JestaRx Group, which provides medical marketing services for clients in the pharmaceutical industry.

JestaRx has received funding from Abbott Laboratories. Two other study authors are employed by and own stock in Abbott, which makes drugs to treat rheumatoid arthritis, the study disclosed.