Smoking, Job Type, Education Level Linked to Inflammation in Axial Spondyloarthritis

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ATLANTA — Smoking may be strongly associated with magnetic resonance imaging-sacroiliac joint (MRI-SIJ) inflammation among patients with axial spondyloarthritis (axSpA) who have blue collar jobs or a low education status,¹ according to study results presented at the 2019 American College of Rheumatology/Association of Rheumatology Professionals (ACR/ARP) Annual Meeting, held November 8 to 13, 2019, in Atlanta, Georgia.

The study included 425 patients with axSpA from the DESIR cohort² who fulfilled the Assessment of SpondyloArthritis international Society axSpA classification criteria. In 1 session, 4 imaging continuous outcomes (x-ray spine [modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS), range 0-72]; x-ray SIJs modified New York grading [mNY, 0-8]; MRI-Spine [Spondyloarthritis Research Consortium of Canada (SPARCC), range 0-414]; and MRI-SIJ [SPARCC, range 0-72]) were scored by 3 central readers; readers scored independently, blinded for time order.

Researchers tested smoking as a binary variable (smoking status since last visit). Socioeconomic variables included age, sex, ethnicity (white vs other), job type based on “collar” (blue [manual labor work] vs white [office-based work]), educational status (low vs high), marital status (married vs not married), and parental status (number of children).

Researchers analyzed interactions between smoking and socioeconomic factors, and models were stratified if statistically (P <.15) and clinically significant interactions were found. They used multivariable, time-varying models that used generalized estimating equations adjusting for possible confounders to assess the effect of smoking on imaging outcomes.

Of the 425 patients with axSpA, 225 (53%) were men, 167 (40%) were smokers, and 287 (68%) had blue collar jobs. At baseline, the mean scores were 4.67±7.85 for MRI-SIJ SPARCC, 2.73±7.95 for MRI-spine SPARCC, 0.39±1.66 for mSASSS, and 1.70±1.84 for mNY.

Researchers found that both smoking and job type were significantly associated with MRI-SIJ inflammation (P =.031) and mNY grading (P =.096) as outcomes. In addition, educational status modified the association between smoking and MRI-SIJ inflammation (P =.026).

Multivariate analysis indicated that smoking was significantly associated with more MRI-SIJ inflammation over 5 years of follow-up in patients with a blue-collar job (β, 3.35; 95% CI, 0.54-6.17). Smoking was also associated with MRI-SIJ inflammation over 5 years in patients with a low education status (β, 2.69; 95% CI, 0.48-4.91). Smoking was not significantly associated with any other imaging outcomes, including sacroiliac joints, spine, and MRI radiographs, over time.

Patients who were men showed a positive association with MRI-SIJ inflammation irrespective of job type, however, MRI-Spine inflammation and structural damage were only associated with patients with blue-collar jobs with SIJ damage.

“These findings suggest a possible role for mechanical stress (seen with manual jobs) amplifying the effect of smoking on axial inflammation in axSpA,” the researchers wrote.

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

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References

1. Nikiphorou E, Ramiro S, Sepriano A, et al. Do smoking and socio-economic factors independently influence imaging outcomes in axial spondyloarthritis? Five-year data from the DESIR cohort. Presented at: 2019 ACR/ARP Annual Meeting; November 8-13, 2019; Atlanta, GA. Abstract 854.

2. Dougados M, d’Agostino MA, Benessiano J, et al. The DESIR cohort: a 10-year follow-up of early inflammatory back pain in France: study design and baseline characteristics of the 708 recruited patients. Joint Bone Spine. 2011;78(6):598-603.