The influence of smoking on treatment response is well known in rheumatoid arthritis, but the impact of tobacco use on patients with axial spondyloarthritis is now beginning to emerge.

A study in this week’s Annals of the Rheumatic Diseases found smokers with axial spondyloarthritis and elevated C-reactive protein (CRP) levels achieved significantly smaller reductions in BASDAI and ASDAS scores after initiation of TNF inhibitors, compared with nonsmokers.

The odds of reaching a 50% improvement in BASDAI score or meeting ASAS criteria for 40% improvement after 1 year was significantly lower in current smokers than in nonsmokers (odds ratio, 0.54; P = .03; and OR, 0.43; P = .004, respectively), found the study of almost 700 patients.

Past smoking had no significant effect on response to treatment, the researchers said.

The underlying mechanisms on the influence of smoking are unclear, but could be related to an interference with the pharmacokinetics of anti-TNFs or smoking may increase pain levels or starve tissues of oxygen, the researchers suggested.

“Whether quitting smoking might ameliorate the course of disease during treatment with TNFi remains to be confirmed in prospective studies,” they concluded.