Background/Purpose: Smoking has been found to be associated with an increased risk of developing psoriatic arthritis (PsA)¹. The purpose of this study was analyse possible associations of smoking habits with self-reported clinical features in a large population based cohort of patients with a diagnosis of PsA.

Methods: All health care seeking subjects with a diagnose of PsA according to ICD 10 codes (given at least once by a rheumatologist/internist or twice by any other physician) were identified by a regional health care register during 2003-2007². In 2009 all identified subjects aged 18 years or older (n=2003) were invited to participate in a cross sectional questionnaire survey. The questionnaire included self-reported data on smoking (never smokers or ever smokers), age at disease onset, physical function (HAQ, 0-3 best to worst), pain, fatigue and global health (numerical rating scales 0-10 best to worst) health related quality of life (EQ-5D, 0-1 worst to best), 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 77% whereof 369 patients (18%) declined participation and 1185 (59%) returned the questionnaire,  mean age 57.5 (SD 13.5) years and 58% were women. 1173 subjects responded to the smoking question whereof 448 (38%) were never smokers and 725 (62%) were ever smokers.

Mean age at disease onset was 42.3 (SD 13.4) years in never smokers vs. 46.0 (SD 13.2) in ever smokers. Never smokers vs. ever smokers had mean HAQ 0.59 (SD 0.6) vs. 0.71 (SD 0.6),  mean pain 3.9 (SD 2.4) vs.4.4 (SD 2.5),  mean fatigue 4.4 (SD 2.8) vs. 5.0 (SD 2.7),  mean global health 3.9 (SD 2.4) vs. 4.4 (SD 2.3), mean EQ-5D 0.68 (SD 0.23) vs. 0.63 (SD 0.26) and mean no of painful regions were 7.2 (SD 4.0) vs. 7.9 (SD 4.3).

The regression analysis showed that ever smokers had worse pain with age-sex adjusted parameter estimates (B) = 0.38 (95% CI 0.09 ; 0.67), worse fatigue B = 0.34 (95% CI 0.02 ; 0.66), worse global health B = 0.36 (95% CI 0.09 ; 0.64), worse EQ-5D B = -0.04 (95% CI -0.07 ; -0.01) and an increased no of painful regions B = 0.54 (95% CI 0.02 ; 1.07) compared with never smokers.

Conclusion: In this population based PsA cohort, patients 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 due to general health perspectives and also due to disease specific issues.