Influence of environmental factors on disease activity in spondyloarthritis: a prospective cohort study.

Objective: Spondyloarthritis (SpA) is a complex inflammatory disorder. We investigated the influence of environmental factors on SpA disease activity.

Methods: A prospective cohort of adults with SpA was followed for 3 years. Patients logged on to a secured Website every 3 months to complete a questionnaire. They reported whether they had been exposed to environmental factors such as stressful or traumatic life events, infections, or vaccinations. Outcome variables included the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), the Bath Ankylosing Spondylitis Functional Index (BASFI), and pain and patient global assessment (PGA) on visual numerical scales (each rated 0-10). Analyses were performed using a generalized estimating equation for repeated measures, adjusted for the outcome variable collected by the previous questionnaire.

Results: In total, 272 patients were included in the analysis, completing the questionnaire on 2240 occasions. The average time (mean ± SD) between 2 connections to the Website was 4.0 ± 2.0 months. Occurrence of life events was followed by an increase of 0.5 (95% CI 0.4-0.7) in the BASDAI, 0.5 (95% CI 0.3-0.6) in the BASFI, 0.7 (95% CI 0.5-0.9) in the PGA, and 0.8 (95% CI 0.6-1.0) for pain (p < 0.0001 for all variations). A moderately statistically significant link was found between vaccination and an elevation of the BASDAI of 0.3 (95% CI 0.0-0.5; p = 0.032). No influence of other factors was detected.

Conclusion: This prospective study in a dedicated SpA cohort shows for the first time a link between stressful events and disease activity. Although this link was statistically highly significant, its clinical meaning remains to be determined because the average magnitude of variation of the different variables studied was rather mild.