You are here
BIRMINGHAM, England -- Smoking was a strong predictor of more severe disease in patients with axial spondyloarthritis (AxSpA), with people who had ever smoked having worse disease activity and worse quality of life than those who had never smoked, researchers reported here.
In addition, current smokers fared worse than those who had quit, according to Sizheng Zhao, of the University of Liverpool, and colleagues.
Zhao's group analyzed data from the British Society for Rheumatology Biologics Register for Ankylosing Spondylitis (BSRBR-AS), and presented their findings at the British Society for Rheumatology (BSR) annual meeting.
"We've known that smoking has a very important role in rheumatoid arthritis, but this is not yet as clear in axial spondyloarthritis," Zhao said. "Many studies so far have demonstrated an association between smoking and disease severity, but not a lot of studies have looked at the amount of smoking and its effect on disease."
Zhao's group looked at the effect of smoking status, amount smoked, and smoking cessation on five widely used disease indices, including the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) -- a requirement for access to biologic therapy in the U.K. -- and the Ankylosing Spondylitis Quality of Life (ASQoL) questionnaire.
This cross-sectional analysis included 932 AxSpA patients in the BSR register who had not yet been treated with biologics. A majority (70%) were men and the mean age was 50. Among patients with available HLA-B27 data, 84% were positive. About one in five were current smokers, 37% were former smokers, and 44% had never smoked. Among the daily smokers, nearly one in four were classified as heavy smokers, smoking more than 10 cigarettes per day.
People who had ever smoked had evidence of worse disease across the measures, after adjusting for age, sex, BMI, and HLA-B27 status, Zhao reported. For example, on the BASDAI, ever smokers had 1 unit score worse disease activity compared to people who had never smoked. Furthermore, people who had quit smoking had better disease activity than those who continued to smoke.
Among current daily smokers, there was a trend toward worse disease severity among people who smoked more cigarettes per day, but this did not reach statistical significance, likely due to the smaller numbers in this comparison, Zhao said.
When the analysis of heavy versus light smoking was stratified by sex, associations differed between men and women. Women who smoked heavily had higher spinal pain visual analogue scores and higher scores on the Bath Ankylosing Spondylitis Functional Index, but not on the other measures.
The primary aim of the ongoing study is to assess whether smoking affects response to anti-tumor necrosis factor (TNF) drugs. That data is not yet ready, but Zhao noted that other studies have seen a deleterious effect.
The BSRBR-AS study did not look at pack-years, which captures the duration of smoking as well as the amount per day. In a second study presented at BSR, Zhao's group looked at the relation between smoking exposure and disease activity in 238 patients who smoked, recruited from a spondyloarthritis specialist service.
In that analysis patients with more than 20 pack-years of smoking exposure had higher scores on disease activity and functional impairment measures. In fact, inactive disease was only seen among current non-smokers and people who had never smoked. The heaviest smokers were more than four times as likely to be in a higher disease activity category than light smokers.
Jon Packham, DM, from Keele University in Stoke-on-Trent in England, noted that socioeconomic status may be a confounding factor, as social deprivation tends to be linked to both high levels of smoking and worse disease. Packham was not involved in the study.
Zhao pointed out that smoking still had a detrimental effect on disease severity after adjusting for education level.
These study findings provide yet another reason to encourage patients with AxSpA to quit smoking, and to do so before they accumulate a large number of pack-years.
"We shouldn't just be recommending smoking cessation as part of health promotion, we should be actively helping these patients to stop, and perhaps we can help by drawing their attention to the effect size," Zhao said.
Based on the trends seen in the heavy versus light smoking analysis, Zhao suggested that even cutting down to less than 10 cigarettes per day may still not be enough to lead to improvements in disease outcomes.
Zhao's recommendation was echoed by Raj Sengupta, MD, from the Royal National Hospital for Rheumatic Diseases in Bath, who spoke on disease management of AxSpA.
A growing body of evidence shows that among people with this more severe form of disease, response to TNF inhibitors, radiographic progression, and survival are worse among smokers, he said. In one study, for example, a man who smoked had an 11.4 times higher chance of progression than a woman who doesn't smoke.
"This is something I say to my male patients who smoke and it seems to actually frighten them to get them to stop smoking ... getting them to stop smoking for a variety of reasons, including radiographic progression and survival, would be key," Gupta stated.