NEW YORK – Smoking worsened the course of axial spondyloarthritis, leading to earlier onset of inflammatory back pain, more severe disease, more frequent inflammation and structural lesions of the sacroiliac joints and spine, and an increased risk of developing severe radiographic sacroiliitis, according to Dr. Christopher T. Ritchlin, who discussed the findings from two studies.
Unlike most other risk factors, smoking is modifiable, noted Dr. Ritchlin, professor of medicine and director of the translational immunology research center at the University of Rochester (N.Y.) Medical Center.
Dr. Christopher T. Ritchlin
The studies involved patients who were in their 30s and early 40s. "These findings help us to focus on the risk factors we should be worried about in [spondyloarthritis (SpA)]," Dr. Ritchlin said at a rheumatology meeting sponsored by New York University.
At the 2011 American College of Rheumatology annual meeting, Dr. Pedro Machado of Leiden (the Netherlands) University Medical Center presented results from the DESIR (Devenir des Spondyloarthropathies Indifferenciées Récentes) cohort, a multicenter study in France (Ann. Rheum. Dis. 2011 Oct. 11 [doi:10.1136/annrheumdis-2011-200180]). This retrospective analysis looked at the records of 654 patients who met at least one set of international criteria for SpA. The patients were young (mean age, 33.6 years) and had back pain of relatively short duration (mean, 1.5 years). About one-third of the patients were classified as smokers, which was determined by physician interview. Information as to whether the patients were current smokers or how much they smoked was not provided. Multivariate analyses were adjusted for age, sex, duration of inflammatory back pain, race, and HLA-B27 status (Rheumatology News, June 2011, p. 38).
Smoking was found to be associated with a significantly earlier onset of back pain (P = .04) and higher disease activity, as measured on both the Ankylosing Spondylitis Disease Activity Index (P = .03) and the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) (P = .003). Those who smoked also had worse functional status, as assessed by the Bath Ankylosing Spondylitis Functional Index (BASFI) (P = .02). Quality of life was impaired for smokers, as measured by the Ankylosing Spondylitis Quality of Life Score (ASQol, P less than .001) and Short Form 36 physical and mental component scores (both P less than .001).
For the first time, smoking was determined to be associated with the presence of MRI inflammation and structural damage, according to Dr. Machado. MRI findings showed that those who smoked had more inflammation of the sacroiliac joints (odds ratio, 1.57; P = .02) and spine (OR, 2.33; P less than .001). Smoking was also associated with more extensive structural lesions of the sacroiliac joints (OR, 1.54; P = .03) and spine (OR, 2.02; P = .01) and a higher modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS, P = .03), a measure of new bone formation.
"Taking into account that smoking is a potentially modifiable lifestyle factor, axial SpA patients who smoke should be strongly advised to quit this habit, as there seem to be disease-specific benefits that go beyond those described for the general population," Dr. Machado said.
Findings from the second study discussed by Dr. Ritchlin showed that smoking was also found to be a risk factor for severe radiographic sacroiliitis in patients with bilateral axial SpA in a cohort study of 151 patients meeting ASAS (Assessment of Spondyloarthritis International Society) criteria for axial SpA (Arthritis Rheum. 2011;63[suppl. 10]:512). Patients were divided into those who had mild disease (sacroilitis less than grade 4, n = 109) and those with more severe disease (sacroiliitis grade 4, n = 42). Most patients were in their late 30s or early 40s, and had the disease for 13 years or more. The study was presented at the 2011 American College of Rheumatology meeting by Grace Yoon of the University of California at San Francisco, where she is in the rheumatology division of the department of medicine.
In a multivariate logistic regression analysis, after adjustment for age and sex, smoking increased the risk of severe radiographic sacroiliitis (OR, 1.13, P = .006). The disease duration also increased the risk of severe radiographic sacroiliitis (OR, 1.07; P = .05) as did nonwhite ethnicity (OR, 3.3; P = .02), total hip arthroplasty (OR, 27.9; P = .0004), and a family history of ankylosing spondylitis (OR, 4.65; P = .01).
"What was really intriguing to me was the finding on MRI that there was an increase in inflammation seen in smokers," said Dr. Ritchlin. "The big question is, How does inflammation lead to osteoproliferation or new bone formation?" He suggested that both genetic factors and mechanobiologic factors such as axial myofascial tonicity influence the process.