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Study Finds Link Between Smoking and Joint Inflammation With Job Type in AxSpA

In patients with axial spondyloarthritis (axSpA), sacroiliac joint (SIJ) inflammation based on magnetic resonance imaging (MRI) findings and smoking are strongly associated with manual labor jobs or low education level, according to results of a new study presented at the 2019 American College of Rheumatology (ACR)/Association of Rheumatology Professionals (ARP) Annual Meeting.

Smoking and systemic inflammation are independently associated with radiographic spinal progression in patients with axSpA. Research suggests certain socioeconomic factors may modify these associations.

To further study this, Elena Nikiphorou, MD, from King’s College London in London, England, and colleagues analyzed data of 417 patients from the Devenir des Spondyloarthrites Indifférenciées Récentes (DESIR) cohort.

The following four imaging continuous outcomes were independently scored by three central readers: spine radiography based on modified Stoke Ankylosing Spondylitis Spinal Score; SIJ radiography based on modified New York criteria (mNY); spine MRI based on the Spondyloarthritis Research Consortium of Canada method; and SIJ MRI based on SPARCC.

The following socioeconomic variables were analyzed: age, gender, ethnicity, job type (manual labor work vs office-based work), educational status, marital status, and the number of children. Smoking status was tested as a binary variable.

Of all the patients, 53% were men (n=225), 40% were smokers (n=167), and 68% held manual labor jobs (n=287).

A significant interaction was found between smoking and job type with MRI SIJ inflammation as the outcome, as well as with mNY grading of SIJ. Similarly, educational status was shown to modify the association between smoking and MRI SIJ inflammation.

Smoking was significantly associated with more MRI SIJ inflammation over 5 years of follow-up only in patients with a manual labor job. These results were similar in patients with a low education level.

Smoking was not significantly associated with any of the other imaging outcomes over time.

The researchers observed a positive association between male gender and MRI SIJ inflammation, regardless of job type. Male gender was also positively associated with MRI spine inflammation and structural damage, although only for patients with manual labor jobs in the case of SIJ damage.

“Smoking and MRI sacroiliac joint inflammation strongly associate over time in patients with blue collar job type or with low education, irrespective of other socioeconomic factors, systemic inflammation, and treatment,” Dr Nikiphorou said during her presentation. “There is suggestion of a possible role for mechanical stress—seen with manual jobs—amplifying the effect of smoking on axial inflammation in axSpA.” —Melinda Stevens

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