Objective: To study whether obesity increases the risk of psoriatic arthritis (PsA), given that obesity is a risk factor for psoriasis and is associated with more severe disease.
Design: Case series. We used Cox regression analysis to study the relationship between obesity and PsA while controlling for age at psoriasis onset, current body mass index (BMI), sex, family history of psoriasis, worst-ever body surface area (BSA) involvement, Koebner phenomenon, and nail involvement.
Setting: Dermatology clinics at the University of Utah School of Medicine. Patients Volunteer sample of patients with dermatologist-diagnosed psoriasis enrolled in the Utah Psoriasis Initiative from November 2002 to October 2008 (943 subjects; 50.2% women, 49.8% men).
Main outcome measures: Physician diagnosis of PsA from self-report questionnaire.
Results: In our subjects, we found that BMI at age 18 years was predictive of PsA (odds ratio [OR], 1.06) (P < .01) over and above control variables. Other variables that were predictors of PsA included younger age at psoriasis onset (odds ratio [OR], 0.98) (P < .01), female sex (OR, 1.45) (P = .01), higher worst-ever BSA involvement with psoriasis (OR, 1.01) (P = .04), Koebner phenomenon (OR, 1.59) (P < .01), and nail involvement (OR, 1.76) (P < .01). Current BMI and family history of psoriasis were not significant predictors of PsA.
Conclusions: This study suggests that obesity at age 18 years increases the risk of developing PsA. Adiposity is associated with higher levels of inflammatory cytokines known to be associated with psoriasis. This inflammatory milieu could increase the risk of PsA in predisposed subjects. Prevention and early treatment of obesity may decrease the risk of PsA.