Absence of an association between gastrointestinal tract surgery and newly diagnosed psoriasis

Background: Gastrointestinal tract surgeries could disrupt the microbiome and simultaneously cause trauma, which may result in psoriasis. Objective: To examine associations between gastrointestinal tract surgeries and newly diagnosed psoriasis. Methods: This nested case-control study included patients with newly diagnosed psoriasis from 2005 to 2013, retrieved from the Taiwan National Health Insurance Research Database. We retrospectively (5 years from the index date) determined whether the patients had undergone gastrointestinal tract surgery. Results: We identified 16 655 patients with newly diagnosed psoriasis and matched 33 310 individuals as the control group. The population was stratified by age and sex. There was no association between age and psoriasis (<20 years: adjusted odds ratio [aOR] 0.80, 95% confidence interval [CI] 0.52-1.24; 20-39 years: aOR 1.09, 95% CI 0.79-1.51; 40-59 years: aOR 0.89, 95% CI 0.57-1.39; ≥60 years: aOR 0.82, 95% CI 0.54-1.26). Similar findings were obtained by sex, with no differences among men (aOR 0.90, 95% CI 0.69-1.17) and women (aOR 0.96, 95% CI 0.71-1.29). Conclusion: Our study indicates that gastrointestinal surgeries have limited age- and sex-related effects on psoriasis. These findings provide new insights into the risk of developing psoriasis.