Current Smoking Associated With Axial Involvement and Radiographic Sacroiliitis in Psoriatic Arthritis

Both axial psoriatic arthritis (axPsA) and radiographic sacroiliitis are more common among current smokers, but not ex-smokers, according to study results published in The Journal of Rheumatology.

Investigators extracted data from the PsA-International Database, a prospective, multicenter registry of adult patients with PsA residing in Canada, Italy, and Turkey. The present study included patients with available smoking data at enrollment. Smoking status was classified as never, current, or ex-smoker, with duration and intensity calculated in pack-years. Smoking data were compared between patients with and without axSpA. Diagnosis of axPsA was made at the clinician’s discretion, based on inflammatory back pain and, if available, radiographs of the sacroiliac joints. Two-group comparisons were made by Fisher’s exact or Chi-square tests. Researchers used multivariable logistic regression to identify predictors of axial involvement. Models were adjusted for risk factors for axial disease, including age, sex, body mass index, disease duration and subtype, disease activity, functioning, and C-reactive protein levels.

A total of 1535 patients with smoking data were included, among whom 562 (36.6%) were men. Mean age at enrollment was 46.9±13.4 years. A total of 454 patients (29.6%) had axPsA. Compared with patients in the non-axPsA group, those in the axPsA group had a younger mean age (47.8 vs 44.7 years) and were more frequently men (33.4% vs 44.3%; both P <.001). Overall, 334 (21.8%) patients were current smokers, 324 (21.1%) were ex-smokers, and 877 (57.1%) had never smoked. Ever smoking was more frequent among patients with axPsA vs non-axPsA (48.2% vs 40.6%; P =.006). Compared with never smoking, current smoking was associated with increased odds of having axPsA (odds ratio [OR], 1.42; 95% CI, 1.07-1.88); however, prior vs never smoking was not significantly associated with axial involvement (OR, 0.97; 0.71-1.31).

Additional predictors of axPsA diagnosis included younger age (OR, 0.98; 95% CI, 0.97-0.99), being men (OR, 1.49; 95% CI, 1.17-1.89), and nail involvement (OR, 1.43; 95% CI, 1.14-1.80). In analyses of patients with available radiographs of the sacroiliac joints (n=187; 41.2%), current smoking was more common among patients with vs without sacroiliitis (39% vs 20%; P =.05). Smoking pack-years were also higher in patients with vs without sacroiliitis (16.7±13.5 vs 10.9±11.5 pack-years; P =.030). In multivariable regression models, current vs never smoking was associated with nearly a 7-fold greater odds of having radiographic sacroiliitis (OR, 6.6; 95% CI, 2.02-21.6).

Overall, axial involvement was more common among current smokers, but not ex-smokers. Sacroiliitis was also strongly associated with current smoking.

The number of patients with complete spinal radiographs was low, preventing further assessment of the relationship between smoking intensity and sacroiliitis. In addition, the cross-sectional study design may have prevented the assertion of causality between smoking and axial involvement.

“If smoking cessation is proven to reduce to risk [for] axPsA in prospective studies, it can be prioritized for the prevention of axPsA among patients with psoriasis,” the investigators wrote.

Disclosure: Study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Solmaz D, Kalyoncu U, Tinazzi I, et al. Current smoking is increased in axial psoriatic arthritis and radiographic sacroiliitis [published online July 1, 2020]. J Rheumatol. doi:10.3899/jrheum.190722