Rheumatoid arthritis may raise the risk of early death by as much as 40 percent, with heart and respiratory problems the most common contributors to a shortened life span, a new study suggests.
And among those who died of respiratory causes, one of the main causes of death was chronic obstructive pulmonary disease (COPD), the researchers reported.
The findings provide new evidence to support previous research suggesting a link between rheumatoid arthritis and increased risk of early death, and they point to the need for doctors to closely monitor these patients, the study authors said.
Read: Diagnosing rheumatoid arthritis
However, the study only showed an association, and not a cause-and-effect relationship, between rheumatoid arthritis and risk of premature death.
Rheumatoid arthritis is an autoimmune disorder in which the body's immune system attacks the joints, resulting in pain and swelling.
About 1.3 million people in the United States have rheumatoid arthritis, and of these, nearly 75 percent are women, according to the American College of Rheumatology.
Read: Dietary care in rheumatoid arthritis
For the study, researchers from Brigham and Women's Hospital in Boston analysed data from 964 women with rheumatoid arthritis who were part of the Nurses' Health Study, and compared them with women without the disease. The study has followed more than 100,000 registered nurses since 1976.
Two types of rheumatoid arthritis
"Previous studies have suggested that rheumatoid arthritis may be associated with increased mortality, but were not able to control for other variables, such as smoking, that affect both rheumatoid arthritis and mortality risks," study corresponding author Dr Jeffrey Sparks said in a hospital news release.
He is with the division of rheumatology, immunology and allergy at the hospital.
Read: Obesity ups rheumatoid arthritis
"Because the Nurses' Health Study is so large and has been following participants for so long, we were able to gather much more information about our subjects we could follow them before and after diagnosis, take their health behaviours into account and determine specific causes of death," he said.
"By doing so, we found strong evidence of increased risk for respiratory, cardiovascular and overall mortality for patients with rheumatoid arthritis," Sparks said.
The researchers also analysed differences between the two types of rheumatoid arthritis: seropositive and seronegative.
Read: Rheumatoid arthritis and your sex life
Those with seropositive rheumatoid arthritis – which typically causes more severe symptoms – were nearly three times more likely to die of respiratory causes than those with seronegative disease, according to the study. It was published in the journal Arthritis Care & Research.
While many doctors know that rheumatoid arthritis patients are at increased risk of death from heart problems, the new findings highlight the need to watch for respiratory symptoms, even among patients who never smoked or are former smokers, Sparks added.
"We hope that this study will encourage patients and clinicians to be more aware that patients with rheumatoid arthritis are at increased risk of both respiratory and cardiovascular mortality, particularly patients with seropositive rheumatoid arthritis," he said.
Lifetime arthritis risk higher than reported
Can the Pill relieve RA symptoms