Prevalence of tobacco smoking and its association with disease severity and psoriatic arthritis among patients with nail psoriasis in China: a cross-sectional study.

Introduction: Nail psoriasis is a common, treatment-refractory manifestation of psoriasis. Smoking is a key environmental factor implicated in nail and articular psoriasis. While smoking's association with cutaneous psoriasis is well-studied, its relationship with nail psoriasis remains less explored. Objective: The primary objective of this study was to investigate the impact of smoking on the severity of nail psoriasis and arthritic psoriasis in patients with nail psoriasis. Methods: Data from 1044 nail psoriasis patients within a population-based registry in China were analyzed. We assessed associations of smoking status and intensity with sociodemographics, disease severity and dermatology quality of life measures (including PASI, BSA, DLQI, and PEST scores), and PsA diagnosis. Analyses used SPSS 29.0; Results: The current smoking rate among patients with nail psoriasis is 34.6%, which is much higher than the current smoking rate among patients without nail psoriasis (20.2%). The proportions of the three different smoking intensities are also much higher than those among patients without nail psoriasis. Current smoking affects the total nail involvement count in patients with nail psoriasis, and severe smoking affects both the total nail involvement count and the nails with > 90% area involvement count in these patients. However, we found that smoking intensity was negatively correlated with DLQI scores in nail psoriasis, which is contrary to previous studies on plaque psoriasis. Spearman's correlation analysis revealed that smoking intensity and smoking index were positively associated with total nail involvement count and individual nails > 90% with area involvement count. In the regression analysis for PSA, the OR for current smokers was 0.57 (95% CI: 0.35-0.92) compared to non-smokers, and the OR for severe smokers was 0.37 (95% CI: 0.15-0.90) compared to mild smokers. Conclusion: Patients with nail psoriasis have higher smoking rates and smoking intensity compared to those without nail psoriasis. The total nail involvement count was higher in current smokers than in non-smokers. Smoking intensity was positively associated with total nail involvement count and individual nails with > 90% area involvement count. Current smoking was a negative associated factor for PEST risk level. Both current smoking and severe smoking were negative associations with the presence of psoriatic arthritis.