Smoking may make some treatments for psoriatic arthritis less effective, according to the results of a recent study.
In an analysis of treatment outcomes for patients taking certain kinds of biologics, a team of Danish researchers found that smokers do not improve as much, and do not stick with the treatment for as long, as nonsmokers.
The study, published last month in Annals of the Rheumatic Diseases, examined the impact of smoking on treatment with the tumor necrosis factor-alpha (TNF-alpha) inhibitor drugs Enbrel (etanercept), Remicade (infliximab) and Humira (adalimumab). A cytokine, or protein, involved in inflammation, TNF-alpha is a common target for psoriatic disease treatments.
Using a Danish patient database called the DANBIO registry, researchers studied 1,148 people taking TNF-alpha inhibitors for psoriatic arthritis. Among this group, 33 percent were current smokers and 41 percent had never smoked. The remaining 26 percent were classified as previous smokers, who stopped smoking by the time they started treatment.
Before starting treatment, smokers were in poorer health than never-smokers or previous smokers, according to the study. They also had been diagnosed with psoriatic arthritis more recently, the researchers report, which could indicate that their symptoms were more aggressive.
After six months of treatment, only 24 percent of smokers improved by 20 percent (a measurement known as ACR20), compared with 33 percent of never-smokers, according to the study results. Using a different measure of improvement, researchers found that only 23 percent of smokers achieved EULAR-good-response after 6 months, compared with 34 percent of never-smokers. EULAR-good-response is determined by the number of swollen and tender joints a patient has.
Researchers also found that smokers stayed on TNF-alpha inhibitors for less time than nonsmokers. The median treatment duration was 1.56 years for smokers, compared with 2.43 years for never-smokers.
Therapy with TNF-alpha inhibitors is generally considered to be an effective treatment for psoriatic arthritis, the researchers note. However, they explain, previous studies have shown that only approximately 60 percent of patients achieve ACR20 while on these drugs. This study indicates that smoking may be a lifestyle factor that can make TNF-alpha treatment less effective.