Smoking does not appear to have protective effects against anterior uveitis attacks in patients with axial spondyloarthritis, according to prospective registry study data.
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Both current and ex-smokers had increased uveitis rates versus never-smokers in the study, suggesting that the supposed protective effect of smoking found in previous axial spondyloarthritis studies was not causal, Sizheng Steven Zhao, MD, and his colleagues reported in the Annals of the Rheumatic Diseases.
“Spurious relationships can emerge when studies restrict to a disease population,” the researchers wrote.
The present analysis by Dr. Zhao and colleagues included 2,420 patients with axial spondyloarthritis in the British Society for Rheumatology Biologics Registry for Ankylosing Spondylitis. Of that group, 632 (26%) had a diagnosis of acute anterior uveitis over a total of 1,457 patient-years of follow-up.
Researchers looked specifically at the number of uveitis episodes per 12-month period, which ranged from 0 to 15 in the overall study cohort.
Current smokers had a 33% higher incidence of acute anterior uveitis episodes versus never-smokers, while ex-smokers had a 19% higher incidence, although the findings did not reach statistical significance, according to the researchers.
Because some studies have suggested that smoking may influence response to biologic therapy, Dr. Zhao and coinvestigators stratified patients into biologic and nonbiologic cohorts. In the biologic cohort, they found a 76% higher incidence per year of uveitis attacks for current smokers versus never-smokers, and a 29% increased incidence for ex-smokers versus never-smokers.
These findings are “consistent with increased risk of uveitis observed among smokers in the general population,” the researchers said. “Although nicotine may have anti-inflammatory properties, cigarette smoking is overall pro-inflammatory.”
Those results provide “yet another line of evidence” that should compel spondyloarthritis patients to quit smoking, the researchers added. Previous studies have suggested that smoking may increase radiographic progression and may reduce response to treatment.
The authors declared no competing interests. The registry study is supported by the British Society for Rheumatology, which has received funding from Pfizer, AbbVie, and UCB for the study.
SOURCE: Zhao SS et al. Ann Rheum Dis. 2019 Apr 20. doi: 10.1136/annrheumdis-2019-215348