Background: In subjects with early axial Spondyloarthritis (SpA) smoking has recently been associated with earlier onset of disease, worse lesions of the sacroiliac joints and in later stages syndesmophyte progression. The aim was to study associations of smoking habits with self-reported information in a large population based cohort of patients with axial SpA.

Methods: A cross-sectional questionnaire survey performed in 2009 included all health care seeking subjects aged >18 years with a diagnosis of SpA according to ICD 10 codes identified by a regional health care register (n=3711). Smoking habits were studied in patients with ankylosing spondylitis (AS, ICD M45) and in patients who fulfilled criteria for “non AS axial SpA” (without having one of AS). Criteria for non AS axial SpA were based on data from the questionnaire: pain for 3 months or more during the last 12 months together with 2 or more features out of 5 (inflammatory back pain, history of psoriasis, uveitis/tendinitis, inflammatory bowel disease or heredity). The questionnaire included data on smoking (never smokers vs. ever smokers), disease activity (BASDAI) physical function (BASFI), general health (BAS-G) all measured with numerical rating scales 0-10 (best to worst), health related quality of life (EQ-5D, 0-1 worst to best), pain, fatigue (numerical rating scales 0-10 best to worst) and number of painful regions noted on a pain mannequin (0-16 best to worst). Linear regression analysis was performed and all data were controlled for sex and age.

Results:

Response rate was 76% whereof 2167 (58%) returned the questionnaire and 18% declined participation in the study. 598 subjects had an AS diagnose and 572 fulfilled the criteria for non AS axial SpA.

The AS group had a mean age of 54 (SD14) years and 35% were women. Never smokers constituted 48% of the AS group. Ever smokers had worse scores in all studied variables compared with never smokers.

The linear regression analysis showed that ever smokers in the AS group had worse self-reported scores in BASDAI with age-sex adjusted parameter estimate (B) = 0.60 (95% CI 0.21 ; 1.00), BASFI B = 0.51 (95% CI 0.11 ; 0.91) and fatigue B = 0.51 (95% CI  0.06 ; 1.00) . There was a tendency to worse scores for ever smokers also in EQ-5D B = -0.04 (95% CI -0.09 ; 0.001)

Mean age in the non AS axial SpA group was 55 (SD 14) years and 68% were women. Never smokers constituted 38% of this group. Also in the non AS axial SpA group the linear regression analysis showed that ever smokers had worse self-reported scores in BASDAI with age-sex adjusted parameter estimate (B) = 0.59 (95% CI 0.23 ; 0.94), BASFI B = 0.59 (95% CI 0.17 ; 1.00), pain B = 0.45 (95% CI 0.08 ; 0.82) and fatigue B = 0.43 (95% CI  0.03 ; 0.83), no of painful areas B = 0.73 (95% CI  0.06 ; 1.46) and also in EQ-5D B = -0.06 (95% CI -0.11 ; -0.002).                                                                                                                                                

Conclusion: In a large population based axial SpA cohort, both patients with AS and non AS axial SpA who were ever smokers reported worse clinical features compared with never smokers. Further longitudinal studies are needed to better understand cause and effect. However, smoking cessation should be recommended not only due to general health perspectives but also due to disease specific issues.

References

¹Smokers in early axial spondyloarthritis have earlier disease onset, more disease activity, inflammation and damage, and poorer function and health-related quality of life: results from the DESIR cohort. Chung HY, Machado P, van der Heijde D, D'Agostino MA, Dougados M. Ann Rheum Dis. 2012 Jun;71(6):809-16.