Tobacco smoking and non-communicable disease comorbidity interactively attenuate PASI ₇₅ response in psoriasis: a prospective study in Shanghai

Introduction Tobacco smoking and non-communicable disease (NCD) comorbidities are positively associated with psoriasis severity, but their combined association with treatment response remains unclear. This study evaluated their interactive associations with PASI75 achievement.Materials and methods We prospectively recruited 551 psoriasis patients from Shanghai Skin Disease Hospital (2022–2024). Treatment efficacy was evaluated from baseline to Week 48. Logistic regression assessed associations of smoking and NCD comorbidities with PASI75, and additive interaction was examined using the relative excess risk due to interaction (RERI).Results Tobacco smoking and NCD comorbidities were present in 51.2% and 42.6% of patients, respectively. Compared with those with both risk factors, patients with neither had higher PASI75 achievement at Weeks 8, 12, 24, and 48. At Week 48, PASI75 rates were 76.9% versus 55.8%, a 21.1% absolute difference. RERI indicated synergistic associations with PASI75 achievement at Week 12 (RERI = 0.71, 95% CI 0.05–2.38) and Week 24 (RERI = 0.80, 95% CI 0.11–2.39).Conclusion Smoking and NCD comorbidities were jointly associated with poorer PASI75 achievement, while their concurrent absence was associated with added therapeutic benefit. These findings support integrating smoking cessation and NCD management into routine psoriasis care.Trial registration Chinese Clinical Trial Registry, ChiCTR2200066894.