Supplementary Material for: Obesity, but Not Metabolic Diseases, Is Associated with Risk of Psoriasis: A Population-Based Cohort Study in Taiwan

Background: Obesity and metabolic diseases including diabetes, hyperlipidemia, and hypertension are reportedly associated with an increased risk of psoriasis. However, few prospective studies have investigated the association of obesity and metabolic diseases with the risk of psoriasis. Objective: To examine whether obesity or metabolic diseases increase the risk of psoriasis. Methods: Participants were collected from 4 rounds (2001, 2005, 2009, and 2013) of the Taiwan National Health Interview Survey. Incident cases of psoriasis were identified from the National Health Insurance database. Participants were followed from the time of the National Health Interview Survey interview until December 31, 2017, or until a diagnosis of psoriasis was made or the participant died. The Cox regression model was used for the analyses. Results: Of 60,136 participants, 406 developed psoriasis during 649,506 person-years of follow-up. Compared to participants with a BMI of 18.5–22.9, the adjusted hazard ratios (aHR) of psoriasis were 1.34 (95% CI 1.05–1.71) for a BMI of 25.0–29.9 and 2.70 (95% CI 1.95–3.72) for a BMI ≥30. Neither individual nor multiple metabolic diseases were associated with incident psoriasis. Participants with a BMI ≥30 were at significantly higher risk of both psoriasis without arthritis (aHR 2.60; 95% CI 1.85–3.67) and psoriatic arthritis (aHR 3.96; 95% CI 1.45–10.82). Conclusion: Obesity, but not metabolic diseases, significantly increased the risk of psoriasis.