A study says 1 in 10 people with rheumatoid arthritis will develop serious lung complications over the course of their disease, making interstitial lung disease, or ILD, as deadly to people with RA as congestive heart failure.

“We already knew that RA patients had a rate of ILD, and I knew that it was reasonably high, but I didn’t know how high. It’s a bit of an 'a-ha' moment,” says Imre Noth, MD, director of the Interstitial Lung Disease Program at the University of Chicago Hospitals, who was not involved in the study.

Interstitial lung diseases are conditions characterized by scarring of the lung tissue. In the case of RA-associated ILD, the scarring is caused when the immune system attacks itself, unleashing friendly fire on the joints and other organs, including the lungs.

When the scarring builds up over time, breathing becomes difficult, and patients may need lung transplants to regain function.

While they’ve long known that ILD can be deadly, doctors say until now, there have been few studies helping them understand how prevalent the diseases are in the U.S. and who is most at risk to get them.

For the current study, which was published in the June issue of Arthritis & Rheumatism, researchers at the Mayo Clinic collected the medical records of 1,206 patients seen by doctors in Rochester, Minn., between 1955 and 1995. Half of the patients were diagnosed with RA, and half were people of the same age and sex who did not develop the disease.

They found that 7.7 percent of people with RA developed an ILD, compared to a 0.9 percent of patients in the non-RA control group, making the risk of developing lung disease almost nine times higher in people with RA than in the general population.

“That’s high. That’s a hefty number,” Dr. Noth says. “You have to understand the interstitial lung diseases are very tough to treat and carry a very high mortality. So if that’s a consideration in RA, which is a reasonably prevalent disease, it’s something you want to keep an eye on.”

Dr. Noth says that patients who are identified with ILD is in its early stages may be helped by medication and can be put on the waiting list for a lung transplant sooner.

Once a patient in the study was diagnosed with an ILD, the average survival was 2.6 years.

Tim Bongartz, MD, a rheumatologist and assistant professor of medicine, who was out of the country and unavailable for comment, writes that based on those numbers, ILD appears to be as deadly for people with rheumatoid arthritis as congestive heart failure, which is currently responsible for about 1 in 8 early deaths in patients with RA.

The study was also able to shed some light on who is most likely to develop an RA-related interstitial lung disease.

Being a man appeared to be the most potent factor. Men in the study had a more than four-fold risk of developing ILD compared to women. Other significant risks included an older age at diagnosis, higher disease activity and treatment with either methotrexate or corticosteroids.

Researchers admit some shortcomings to their study, too. For one, participants were mainly white, so they don’t know if their results would be replicated in a more ethnically diverse group.

The research team also writes that it’s tough to come up with a clear definition of ILD, since it currently includes a variety of different types of lung disease.

Dr. Noth says while it is nice to know how often this is happening, he would like future research to look at why it’s occurring, to better understand the mechanisms at play. But he says as far as he’s concerned, these new findings raise the question now of what, if any preventative screening the medical community should be doing.

“Its not that we didn’t know it was happening, but I didn’t know it was 10 percent,” he says. “ Should we be screening these patients on a regular basis? Do you want regular CT scans, maybe yearly or regular pulmonary function tests to see if they are developing an interstitial lung disease which could be terminal?”

Until the medical community makes those decisions, he says this will be an individualized issue, so he stresses that if RA patients are short of breath, they need to talk with their doctor and get evaluated.