medwireNews: Asthma is associated with elevated levels of anti-citrullinated protein antibodies (ACPA) and the development of seropositive rheumatoid arthritis (RA), researchers report.
“These findings suggest that individuals with asthma may be susceptible to developing RA,” say Jeffrey Sparks (Brigham and Women’s Hospital, Boston, Massachusetts, USA) and co-investigators.
Among 96 women from the Nurses’ Health Study (NHS) and NHSII who had elevated ACPA levels an average of 9.7 years prior to developing RA, 17.7% reported having clinician-diagnosed asthma at the time of blood draw.
By comparison, just 6.3% of 286 controls matched for age and time of day at blood draw, cohort, fasting, menopausal status, and postmenopausal hormone use reported having asthma. These findings translated into a significant odds ratio (OR) for asthma of 3.57 among patients with versus without pre-RA ACPA positivity after adjustment for matching factors, active and passive smoking, and BMI.
Sparks and team note in Arthritis Research & Therapy that this association remained consistent when the analysis was restricted to people who had never smoked (adjusted OR=4.62) or those who had pre-RA ACPA positivity within 5 years of RA diagnosis (OR=4.29).
And when the researchers evaluated serology at the time of RA diagnosis, the presence of asthma was significantly associated with seropositive RA (OR=1.79), but not with RA overall or with seronegative RA.
“Overall, these results indicate that diseases of chronic airway inflammation may be important in RA pathogenesis, contributing to ACPA development in the years preceding clinical RA onset,” say the researchers.
On the other hand, they suggest “[i]t is also possible that subclinical pulmonary mucosal injury related to ACPA development may pre-dispose patients to clinical lung diseases at a later point in the preclinical RA phases, or after articular RA onset,” and recommend that the potential bidirectional association should be investigated in future studies.
Sparks and team note that they were unable to investigate the association between asthma subtypes or disease duration and RA, and that “[f]uture studies are needed to understand how different asthma phenotypes or their treatment may differently affect RA risk.”
Moreover, “the study was comprised of female nurses who were mostly healthy, white, educated, and working at baseline, [and] the sample may not be generalizable to other populations,” they add.
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