Smoking and delay to diagnosis are associated with poorer functional outcome in psoriatic arthritis

Objective To identify predictors of poorer physical function in established psoriatic arthritis (PsA). Methods PsA patients with disease duration of 10years were identified from the Bath longitudinal cohort. Physical function was assessed using the Stanford Health Assessment Questionnaire (HAQ). Sex, age at diagnosis, duration of symptoms prior to diagnosis, smoking, treatment and year of diagnosis were included in a multivariable regression analysis to identify associations with HAQ. Results 267 patients were identified for inclusion. The median age was 56years (IQR 45-63), median disease duration was 13years (IQR 10-18) and median HAQ score was 0.63 (IQR 0.13-1.25). The model predicted significant increases in HAQ related to smoking (0.23, 95% CI 0.04 to 0.42), age >50years at diagnosis (0.27, 95% CI 0.03 to 0.51), symptom duration of 1year before diagnosis (0.22, 95% CI 0.02 to 0.42), female sex (0.39, 95% CI 0.20 to 0.57) and history of treatment with an anti-TNF agent (0.63, 95% CI 0.32 to 0.93) at follow-up. Conclusions Smoking, delay to diagnosis, older age at diagnosis, female sex and a history of anti-TNF treatment are associated with worse physical function in established PsA.