CHICAGO – The risk of both interstitial and obstructive lung disease is increased in patients with rheumatoid arthritis, as is mortality in affected, compared with unaffected, arthritis patients.
In a cohort of rheumatoid arthritis (RA) patients from a single county in Minnesota who have been followed since 1955, the risk of developing interstitial lung disease is about 8%, compared with less than 1% in the general population, Dr. Eric Matteson reported at a symposium sponsored by the American College of Rheumatology.
"The hazard ratio for developing interstitial lung disease, compared to non-RA patients, is about a ninefold increase, so this is an enormous difference," said Dr. Matteson, professor of medicine and chair of the division of rheumatology and health sciences research at the Mayo Clinic, Rochester, Minn.
Furthermore, these patients with interstitial lung disease have much higher mortality than RA patients who do not have interstitial lung disease (hazard ratio 2.14), he said.
The findings compare well with those from a recently completed survey, which used National Center for Health Statistics data and suggested that, while mortality in RA in general has declined, the rates of interstitial lung disease are increasing.
"We’re probably seeing more [interstitial lung disease in RA patients] today than we did maybe 10, 20, and certainly 30 years ago," Dr. Matteson said.
It is possible that the declines in RA mortality overall are outpacing those from interstitial lung disease. Although biologics being used to treat RA are helping joint disease and other extra-articular manifestations of RA, there is no evidence that they influence the development of interstitial lung disease, he suggested.
Obstructive lung disease is also a concern in RA patients, and although the difference in incidence between RA patients and the general population is smaller than with interstitial lung disease, this finding may be more surprising, Dr. Matteson said, noting that this information from the Minnesota cohort was new to him.
"It appears that rheumatoid arthritis is a risk factor for obstructive lung disease," he said. After correcting for age, sex, and smoking status, there is about a 50% increase in the incidence of obstructive lung disease in RA patients, compared with the general population.
The reason for this is unclear, but "intriguing new data" suggest that the cystic fibrosis genes and some related genes are risk factors for developing bronchiolitis and other forms of obstructive disease in RA, so that may be part of the biologic answer, he said.
There is a biologic reason why these patients also may be at higher risk for obstructive lung disease as well as interstitial lung disease, he said.
And like interstitial lung disease, obstructive lung disease also adversely affects mortality in RA patients (hazard ratio of 1.87 for affected vs. nonaffected RA patients), he noted.