Smoking reduces risk for psoriatic arthritis in psoriasis patients

Smoking may reduce the risk for psoriatic arthritis (PsA) in patients with psoriasis, say researchers, but not in patients who are positive for the human leukocyte antigen (HLA) allele HLA-C*06.

Around one-third of all patients with psoriasis subsequently develop PsA, a debilitating inflammatory condition.

Smoking has been shown to suppress inflammation and have a protective effect against the symptoms of disorders such as ulcerative colitis. Dafna Gladman (University of Toronto, Ontario, Canada) and colleagues therefore investigated whether it may also have a protective effect against PsA in psoriasis patients.

In total, 728 patients with PsA and psoriasis and 404 patients with psoriasis alone were included in the study.

The researchers found that there were more current and former smokers in the psoriasis alone group compared with the PsA group, at 30.2% versus 23.4% and 26.7% versus 22.3%, respectively.

Multivariate analysis adjusting for age, gender, level of education, and alcohol consumption, showed that current smokers with psoriasis had a significant 43% lower relative risk for developing PsA than lifetime nonsmokers.

There was no significant difference in risk for PsA between former smokers and never smokers after adjusting for potential confounders, however.

Of note, smoking did not influence risk for PsA in a subgroup of psoriasis patients who were positive for the HLA-C*06 allele, the strongest known genetic predictor for psoriasis.

"In this exploratory case-control study we have found a signal for an inverse association between current smoking and PsA compared with patients with psoriasis alone," write Gladman et al in the Annals of Rheumatic Diseases.

"Additional studies that investigate environmental risk factors for PsA and gene environment interaction are required to confirm our results," they conclude.



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