Abstract
Objective
Increasing psoriasis severity has been associated with comorbidities including cardiovascular disease. The objective of this study was to examine the association of psoriasis severity with the development of psoriatic arthritis (PsA).
Methods
A prospective population-based cohort study was performed within The Health Improvement Network, a United Kingdom medical record database. Patients aged 25–60 years with a code for psoriasis were randomly selected between 2008–2011. Questionnaires were sent to their general practitioners to confirm the diagnosis of psoriasis and provide the patient’s approximate body surface area (BSA). Incidence of PsA was calculated by BSA, and Cox proportional hazard ratios were used to examine the risk of developing PsA by BSA category after adjusting for other covariates.
Results
Among 10 474 questionnaires sent, 9,987 (95%) were returned, 9,069 (91%) had confirmed psoriasis, and BSA was provided for 8,881 patients: 52% had mild psoriasis, 36% moderate psoriasis, and 12% severe psoriasis. The mean age was 46, and 49% were female. Mean follow-up time was 4.2 years (SD 2.1); the incidence of PsA was 5.4 cases per 1,000 person years. After adjusting for age and sex, BSA >10% (HR 2.01, 95% CI: 1.29–3.13), BSA 3–10% (HR 1.44, 95% CI: 1.02–2.03), obesity (HR 1.64, 95% CI: 1.19–2.26), and depression (HR 1.68, 95% CI: 1.21–2.33) were associated with incident PsA.
Conclusions
In this large prospective cohort study, BSA assessed by general practitioners was a strong predictor of developing PsA, and obesity and depression were additive risk factors.