In the journal Arthritis Care & Research, the researchers describe how they found that patients with rheumatoid arthritis had a 47 percent higher risk of being hospitalized with chronic obstructive pulmonary disease (COPD) than the general population.
Rheumatoid arthritis is an autoimmune disease — that is, it develops because the immune system wrongly attacks healthy tissue, mainly in the joints. As a result, the lining of the affected joints — commonly the knees, hands, and wrists — become inflamed, causing pain and swelling.
The disease can also attack tissue in the rest of the body, including muscle, tendons, connective tissue, and fibrous tissue, and it can affect the heart, lungs, and eyes.
Estimates suggest that up to 1 percent of people around the world have rheumatoid arthritis, with women and those in developed countries being the most affected.
COPD linked to inflammation
As it progresses, COPD causes coughing — accompanied by large amounts of mucus — and other symptoms, such as shortness of breath, wheezing, and chest tightness.
Reports suggest that 6.4 percent of people in the United States have been diagnosed with COPD, and that there may be more who are not aware that they have it.
While smoking is the main cause of COPD, up to 25 percent of patients who develop it have never smoked.
Other factors that are known to raise the risk of COPD include air pollution, chemical fumes, and other lung irritants such as some types of dust. A rare genetic disorder called alpha-1 antitrypsin deficiency can also be a factor.
In their study paper, senior author Diane Lacaille — a professor in the Division of Rheumatology at the University of British Columbia in Canada — and colleagues note that previous studies have shown that there is a link between COPD and inflammation.
As rheumatoid arthritis is a prolonged, inflammatory condition, they wondered whether it might make people who have it more likely to develop COPD.
Higher rate of COPD hospitalization
To investigate further, the team looked at data on the population of British Columbia, comparing records on 24,625 patients diagnosed with rheumatoid arthritis between 1996 and 2006 with 25,396 randomly selected, matched individuals from the general population (the controls).
The results showed that there was a higher rate of hospital admission for COPD among patients with rheumatoid arthritis than in the general population.
After ruling out other potential influencing factors, the researchers calculated that individuals with rheumatoid arthritis had a 47 percent higher risk of being hospitalized with COPD than the controls.
"The increased risk remained significant after modeling for smoking and with varying COPD definitions," write the authors.
'Look out for early COPD symptoms'
Prof. Lacaille notes that doctors with patients who have rheumatoid arthritis may not realize that they have a higher risk of COPD.
"These findings are novel," she explains, "because it has only recently been recognized that inflammation plays a role in the development of COPD."
People living with rheumatoid arthritis, as well as the clinicians who care for them, need to look out for early symptoms of COPD, so that treatment begins before the lungs suffer irreversible damage, urges Prof. Lacaille.
Such measures should improve prospects for patients and reduce medical costs.
The team notes that the findings also highlight a need to address smoking and other risk factors for COPD in patients with rheumatoid arthritis.
"Our results emphasize the need to control inflammation, and in fact to aim for complete eradication of inflammation through effective treatment of rheumatoid arthritis."
Prof. Diane Lacaille