Rheumatoid arthritis (RA) was found to be associated with an increased risk for restrictive and obstructive pattern abnormalities on spirometry, which were not explained by confounding factors such as smoking, according to study results published in Arthritis & Rheumatology.
Researchers sought to evaluate the type and severity of pulmonary patterns on spirometry among patients with RA compared with control participants from the general population.
A cross-sectional study was conducted that included individuals who underwent spirometry performed by respiratory therapists for research purposes in the UK Biobank.
Co-primary study outcomes were spirometric abnormalities (a restrictive or an obstructive pattern). A restrictive pattern was defined as no obstructive pattern (ie, forced expiratory volume in 1 second/forced vital capacity [FEV1/FVC] ≥0.7) and FVC % predicted less than the calculated limit of normal of FVC. Secondary outcomes included continuous % predicted FEV1, FVC, FEV1/FVC, and forced expiratory flow at 25% to 75% (FEF25-75), as well as the level of severity (mild, moderate, or severe) for a restrictive or an obstructive pattern.
A total of 350,776 participants were included in the study sample of individuals who underwent spirometry. Mean participant age was 56.3±8.1 years; 55.8% were women; 45.5% were ever smokers. From the study sample, a total of 2008 cases of RA were identified. Compared with the control participants, patients with RA were more likely to be older, women, ever smokers, have higher smoking pack-years, and have a history of chronic respiratory disease (ie, asthma, chronic obstructive pulmonary disease, interstitial lung disease, bronchiectasis, and idiopathic pleural fibrosis).
Study results showed that the proportion of restrictive patterns in patients with RA and the general population were 18.1% and 14.1%, respectively. In addition, obstructive patterns were detected in 19.1% of patients with RA and 13.9% of the general population.
The presence of RA was associated with a statistically significant lower % predicted FEV1 (-2.93; 95% CI, -3.63 to -2.24), % predicted FVC (-2.08; 95% CI, -2.72 to -1.45), FEV1/FVC (-0.008; 95% CI, -0.010 to -0.005), and FEF25-75 (-4.79; 95% CI, -6.08 to -3.49) compared with control participants, when adjusted for age, sex, smoking pack-years, smoking status, and body mass index.
Patients with RA vs control participants had a multivariable odds ratio (OR) of 1.36 (95% CI, 1.21-1.53) for a restrictive pattern and an OR of 1.31 (95% CI, 1.16-1.47) for an obstructive pattern. Further, patients with RA vs control participants had an increased risk for mild, moderate, and severe restrictive patterns (OR, 1.29 [95% CI, 1.12-1.49]; OR, 1.45 [95% CI, 1.20-1.75]; and OR, 1.86 [95% CI, 1.08 to 3.23], respectively). In addition, patients with RA vs control participants had an increased risk for moderate and severe obstructive patterns (OR, 1.49 [95% CI, 1.29-1.72] and OR, 1.54 [95% CI, 1.10-2.16], respectively).
A major limitation of the study was that the definition of RA was based on self-report and current treatment with RA-specific medications, with self-report possibly prone to misclassification.
Researchers concluded, “In addition to restrictive lung disease, clinicians should also be aware that airflow obstruction may be a pulmonary manifestation of RA.”
Prisco L, Moll M, Wang J, et al. Relationship between rheumatoid arthritis and pulmonary function measures on spirometry in the UK Biobank. Arthritis Rheumatol. Published online May 13, 2021. doi:10.1002/art.41791