PARIS – Patients with ankylosing spondylitis who worked at more physically-demanding jobs showed greater radiographic progression than did patients who performed more sedentary jobs in a prospective cohort study with 136 patients.
The findings immediately raised questions about "our commonly given advice to patients with spondylarthritis to strenuously exercise. Should physically demanding labor be discouraged?" asked Dr. Sofia Ramiro at the annual European Congress of Rheumatology.
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Stress on the spine may have an impact on the progression of ankylosing spondylitis.
Dr. Ramiro stressed that the finding needs confirmation from studies in other cohorts of patients with ankylosing spondylitis (AS), but it raises the possibility that certain stresses and loads on the spine, from work or exercise, can worsen disease severity.
"If we can confirm that mechanical stress has an impact on radiographic progression, then I think we would have to analyze further and identify the type of activity having this impact, and then recommend the activity not be done," said Dr. Ramiro, a researcher at the Amsterdam Rheumatology Center, University of Amsterdam.
"I’m not saying that we would stop recommending exercise and that patients with AS should stay quiet at home, but perhaps we will advise against certain types of exercise," Dr. Ramiro said in an interview.
Dr. Ramiro and her associates previously reported this year that disease activity contributed longitudinally to radiographic AS progression during up to 12 years of follow-up (Ann. Rheum. Dis. 2014 [doi:10.1136/annrheumdis-2014-205178]). They further evaluated patients in the same cohort, 184 AS patients enrolled in OASIS (the Outcome in AS International Study), for additional factors that might affect radiographic progression either directly or indirectly. In addition to documenting a link between disease activity and radiographic progression, the report earlier this year had identified sex and disease duration as modifiers of the impact of disease activity. This impact on radiographic progression was greater in men, and early during the course of AS.
The new analysis looked for possible effects from smoking, and for chronic activity patterns using the surrogate marker of job type. The 184 patients in OASIS were sorted by their type of regular work, which identified 65 people with physically demanding (blue collar) jobs and 71 with relatively sedentary (white collar) jobs. The other 48 patients had either missing employment data or jobs with less clear links to activity levels, such as students or homemakers.
Dr. Sofia Ramiro
The findings showed that neither smoking nor job type appeared to have a direct influence on radiographic progression, but that smoking and a physically demanding job each had significant indirect effects. A physically demanding job linked with a 1.19-U increase in a measure of radiographic progression (the modified Stoke AS Spine Score, or mSASSS) for every 1-U increase in a measure of disease activity (the AS disease activity score, or ASDAS) during 2 years of follow-up, Dr. Ramiro reported. In contrast, the impact of a sedentary job was a 0.20-U rise in mSASSS for each 1-U rise in ASDAS. Smoking produced a 1.95-U rise in the mSASSS for each 1-U rise in ASDAS, significantly more than the 0.35 rate among nonsmokers.
Personal income, family income, and education each showed no statistically significant link with radiographic progression.
When the investigators analyzed job activity in subgroups divided by sex, they found that the relationship between a more physically demanding job and increased radiographic progression remained statistically significant in men, but the relationship was no longer significant in women.
The researchers could not include leisure activity or sports participation in their analysis as these data were not available. In addition, analysis by leisure activity may pose problems because baseline data on leisure activity may not extrapolate long-term, and patients can also have recall bias when reporting leisure activity, Dr. Ramiro said.
Dr. Ramiro said that she had no disclosures.
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