Obesity and risk of incident psoriatic arthritis in US women

Objectives Both overall and central obesity have been associated with the risk of psoriasis in a prospective study. Data on the association between obesity and psoriatic arthritis (PsA) have been sparse and no evidence on obesity measures and the risk of incident PsA is available now. This study aimed to evaluate the association between obesity and the risk of incident PsA in a large cohort of women. Methods 89 049 participants were included from the Nurses Health Study II over a 14-year period (1991-2005). Information on body mass index (BMI), weight change and measures of central obesity (waist circumference, hip circumference and waist-hip ratio) was collected during the follow-up. The incidence of clinician-diagnosed PsA was ascertained and confirmed by supplementary questionnaires. Results 146 incident PsA cases were identified during 1 231 693 person-years of follow-up. Among all participants, BMI was monotonically associated with an increased risk of incident PsA. Compared with BMI less than 25.0, the RR was 1.83 for BMI 25.0-29.9 (95% CI 1.15 to 2.89), 3.12 for BMI 30.0-34.9 (95% CI 1.90 to 5.11) and 6.46 for BMI over 35.0 (95% CI 4.11 to 10.16). There was a graded positive association between weight change from age 18 years, measures of central obesity and risk of PsA (p for trend <0.001). The analysis among participants developing psoriasis during follow-up revealed a similar association (p for trend <0.01), indicating an increased risk of PsA associated with obesity among patients with psoriasis. Conclusion This study provides further evidence linking obesity with the risk of incident PsA among US women.