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 ≥10 years 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 56 years (IQR 45-63), median disease duration was 13 years (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 >50 years at diagnosis (0.27, 95% CI 0.03 to 0.51), symptom duration of ≥1 year 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.