Psoriasis: prognostic factors and self-assessment

Abstract

The overall aim of this thesis was to explore whether cardiorespiratory fitness (CRF) and stress resilience levels in adolescence predict the risk of developing psoriasis, and whether bariatric surgery affects the prognosis of psoriasis. A further aim of the thesis was to develop a Swedish version of a self-assessment tool for psoriasis.

Papers I and IV: Cohorts of conscripted men (n=1,228,562 in paper I and n=1,669,422 in paper IV) were created using the Swedish Military Conscription Register (SMCR). Through linkage to other Swedish health care registers, incident psoriasis cases were identified. Cox regression analysis adjusted for confounders showed that adolescent men in the lowest CRF (paper I) and stress resilience (paper IV) categories had an increased risk of psoriasis (adjusted hazard ratios (HRs) with 95% confidence intervals (CIs) 1.35 (1.26–1.44) and 1.31 (1.26–1.36), respectively) when using the highest levels as standard. Paper II: Psoriasis patients operated with bariatric surgery (cases) and non-operated psoriasis patients (controls) were identified by merging data from the Swedish National Register for Systemic Treatment of Psoriasis (PsoReg) and the Scandinavian Obesity Surgery Registry (SOReg). The study showed no statistically significant difference in mean change in Psoriasis Area Severity Index (PASI) and Dermatology Life Quality Index (DLQI) scores when comparing cases (n=50) with controls (n=91). Paper III: The original English version of the self-administered PASI (SAPASI) was translated into Swedish using back translation. In 51 subjects, the correlation between the total SAPASI score and the total PASI score was r=0.60 (p<0.0001), with a test–retest reliability of r=0.70 (p<0.0001), n=38. The total SAPASI score exceeded the total PASI score by an average of 0.88+/-3.7 units.

This thesis suggests that low CRF and low stress resilience are associated with an increased risk for psoriasis; that bariatric surgery does not seem to have any additive treatment effects on PASI and DLQI scores in systemically treated patients; and that the Swedish SAPASI is a valid and reliable assessment tool.