LONDON – Patients with rheumatoid arthritis have a high risk of concomitant chronic obstructive pulmonary disease, according to data from two studies.
In one of the studies – which involved more than 15,000 patients with rheumatoid arthritis (RA) and 15,000 healthy individuals as case-matched controls – the risk of the long-term lung condition was 8.9% vs. 4.4%, respectively (P less than .001).
Dr. Suzanne Verstappen
Other data, from the Norfolk Arthritis Register (NOAR) showed that the prevalence of chronic obstructive pulmonary disease (COPD) in patients with inflammatory polyarthritis (IP) or RA was 7.3% (n = 425) at 15 years’ follow-up. Prevalence of the respiratory disease was again doubled when compared to the general population.
"Lung involvement is a common extra-articular manifestation in rheumatoid arthritis," said Dr. Suzanne Verstappen, who presented the findings from the NOAR at the annual European Congress of Rheumatology.
"As could be expected, age and gender were associated with obstructive and restrictive lung disease," said Dr. Verstappen, a research fellow at the Arthritis Research UK Epidemiology Unit at the University of Manchester, England, where the NOAR is coordinated.
Validated spirometry parameters and the Medical Research Council respiratory symptoms questionnaire were used to identify patients with IP or RA who also had COPD. The latter was distinguished from restrictive lung disease whereby the lungs are restricted by the extent that they can inflate. The prevalence of restrictive lung disease was 9.7%.
COPD was observed in 7.3% of the population at 15 years, with higher prevalence rates found in men versus women over the age of 45 years (12.7% vs. 6%, respectively) in a crude comparison. Published rates for the U.K. general population without IP or RA are 6.8% and 3.9% (Popul. Health Metr. 2007;5:8).
Like RA, COPD is a chronic and often debilitating disease. The disease manifests later in life and treatment is symptomatic rather than curative, as the obstruction in the airways is permanent and not usually reversible with bronchodilator therapy. Unlike RA, however, which has multiple etiologic factors and autoimmunity at its root, COPD is almost always caused by smoking. In the NOAR analysis, 53% of the 425 patients were ex-smokers and 13% were current smokers; 34% had never smoked.
Data from the first study, presented during a poster session by Dr. Howard Amital of Sheba Medical Centre in Tel Hashomer, Israel, showed, however, that even with smoking out of the equation, the risk of COPD in patients with RA was higher than in the general population.
Indeed, multivariate analysis showed that RA was associated with COPD after the researchers controlled for confounding factors such as age, gender, smoking, obesity and socioeconomic status.
"The strength of the association increased," Dr. Amital and colleagues reported, with an adjusted odds ratio (OR) of 2.015 (95% confidence interval 1.83-2.22; P less than .001) and an unadjusted OR of 1.89 (95% CI 1.74-2.05, P less than .0001).
The case-control study involved 15,766 patients with RA and 15,240 age- and sex-matched healthy individuals without RA. The study also found higher rates of other chronic disease in patients versus controls, including diabetes (23.9% vs. 19.8%, P less than .0001), ischemic heart disease (19.5% vs. 15.4%, P less than .0001), and heart failure (6.3% vs. 4.3%, P less than .0001).
"This study corroborates the hypothesis that COPD and RA are closely interrelated," Dr. Amital and his team concluded.
NOAR is funded by Arthritis Research UK. Dr. Verstappen and Dr. Amital and colleagues had no conflicts of interest to declare.