Q&A: Smoking and Inflammation in Axial Spondyloarthritis

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Elena Nikiphorou, M.B.B.S./B.Sc., M.D. (Res)

Patients with axial spondyloarthritis who smoke may be more likely to have sacroiliac joint inflammation if they have a blue-collar job or low education, according to a study recently published in Arthritis & Rheumatology. In this Q&A with study author Elena Nikiphorou, M.B.B.S./B.Sc., M.D.(Res), a consultant rheumatologist at King's College Hospital in London, U.K., we discuss the study and its findings.

In patients with axial spondyloarthritis, smoking has been shown in the DESIR study to be associated with higher disease activity and increased axial inflammation and structural damage, but the relationships of smoking, inflammation and radiographic progression are not fully understood. Meanwhile, certain socioeconomic factors may play a role, with physically demanding jobs associated with structural damage and inflammation. However, the long-term effects of smoking or social economic factors on axial inflammation are largely unknown. Dr. Nikiphorou and colleagues investigated the relationship between smoking and imaging outcomes over five years in 406 patients with axial spondyloarthritis and assessed if socioeconomic factors influenced these relationships.

What are the main findings from the study?

We found smoking to be significantly associated with more magnetic resonance imaging-sacroiliac joint (MRI-SIJ) inflammation over five years only in patients with blue-collar jobs, in other words, physically demanding jobs. A similar effect was found in patients with low education. These effects of smoking were independent of other socioeconomic factors, systemic inflammation or treatment.

The findings support a possible role for mechanical stress e.g. as seen with physically demanding jobs, amplifying the effect of smoking on SIJ inflammation in axial spondyloarthritis, in line with previous findings of translational research.

Our study demonstrates associations between smoking and structural damage, spinal and SIJ inflammation, the latter exclusively in patients with blue-collar professions or low education. The association between smoking and inflammation especially at the pelvic level, was much stronger than that with structural damage.

Why do you think smoking was associated to a greater extent with inflammation than structural damage?

Smoking has a well-known link with inflammation in several disease settings. It should be noted that there was generally little amount of damage present in this early axial spondyloarthritis cohort and limited imaging changes over time, which may have prevented the proper investigation of the effect of smoking and potentially also socioeconomic factors on damage variables.

Why would smoking exacerbate inflammation in the pelvic region more than the spine?

This would be subject to speculation and it is not possible to talk about causal links. It’s difficult to know whether smoking or blue-collar cause more pelvic inflammation directly, or through another factor.

Does job type rather than education level play a larger part in the findings?

Both showed similar trends, but strongest effect seen with type of job.

Does smoking or socioeconomic status play a larger part in inflammation in this population?

What we can say is that manual (blue-collar) jobs and consequently mechanical stress, amplifies the effect of smoking on axial inflammation in axial spondyloarthritis, with similar effects seen with low education.

How can the study findings help clinicians and benefit patients?

This study provides new insights into the intricate relationships between smoking, axial damage and socioeconomic factors in axial spondyloarthritis. Being aware of these factors (and socioeconomic characteristics) and these associations can be very relevant in routine clinical practice as they can inform and enable a more holistic and individualistic approach to patient management.

Do you have anything else to add?

Our findings support those of translational research, but they also reinforce the message that further exploring the path of mechanical stress and inflammation is relevant and necessary in this field.

Our study provides greater insights into potential mechanistic links between mechanical stress, smoking and inflammation and calls for more research into this field, including the study of the type and intensity of physical activity that may enhance disease progression and lead to adverse imaging consequences in axial spondyloarthritis.

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REFERENCE

Elena Nikiphorou, Sofia Ramiro, Alexandre Sepriano,et al. “Do smoking and socioeconomic factors influence imaging outcomes in axial spondyloarthritis? Five‐year data from the DESIR cohort.”Arthritis & Rheumatology. June 20, 2020. https://doi.org/10.1002/art.41408