The night matters: sleep quality and evening chronotype associated with clinical severity of psoriasis.

Introduction: Psoriasis is a chronic inflammatory skin disease associated with metabolic dysfunction and obesity. Poor sleep quality appears more prevalent in psoriasis, yet the role of chronotype remains largely unexplored. We evaluated whether patients with psoriasis more frequently exhibit poor sleep quality and evening chronotype compared with healthy controls and assessed the impact of these factors on psoriasis clinical severity. Methods: In this cross-sectional study, 213 adults with psoriasis and 213 age- and sex-matched healthy controls were included. Anthropometric measures (body mass index [BMI], waist circumference [WC]), metabolic indices (fatty liver index [FLI], visceral adiposity index [VAI]), inflammation (C-reactive protein [CRP]), sleep quality (Pittsburgh Sleep Quality Index [PSQI]), and chronotype (Morningness-Eveningness Questionnaire [MEQ]) score were assessed. Psoriasis clinical severity was evaluated using the Psoriasis Area Severity Index (PASI). Results: Compared with controls, patients with psoriasis showed poorer sleep quality (PSQI 9.3 ± 4.9 vs 6.8 ± 4.7 score; p < 0.001) and lower MEQ scores (39.2 ± 19.8 vs 43.1 ± 19.2 score; p = 0.032), indicating a tendency toward the evening chronotype. Within the psoriasis cohort, poor sleepers (PSQI score > 5) had significantly higher PASI than good sleepers (PSQI score ≤ 5; 10.3 ± 6.51 vs 2.3 ± 1.6 score; p < 0.001). Evening chronotype patients exhibited the highest PASI score (11.1 ± 6.3 score), exceeding both morning (1.7 ± 1.1 score) and intermediate chronotypes (3.9 ± 1.2 score) (all p < 0.001). PASI score correlated positively with BMI (r = 0.383), WC (r = 0.478), PSQI score (r = 0.766), CRP levels (r = 0.435), FLI score (r = 0.457), and VAI score (r = 0.627), and inversely with MEQ score (r = -0.781) (all p < 0.001). Stepwise multiple regression identified MEQ score, PSQI score, FLI score, VAI score, CRP levels, WC, and smoking status as independent predictors of PASI score, explaining 81% of its variance (adjusted R² = 0.806). MEQ score showed the strongest independent inverse association with PASI score (p < 0.001). PSQI score (p < 0.001), VAI score (p < 0.001), CRP levels (p < 0.001), WC (p = 0.049), and smoking status (p = 0.009) were positively associated with PASI score, while FLI score showed a modest inverse association (p = 0.019). ROC analysis showed a PSQI score > 10 predicted a moderate-to-severe PASI score (sensitivity 75.7%, specificity 83.9%, AUC 0.856, p < 0.001), while a MEQ score ≤ 25 showed higher accuracy (sensitivity 98.6%, specificity 90.9%, AUC 0.979, p < 0.001). Conclusion: Patients with psoriasis more frequently display poor sleep quality and evening chronotype compared to healthy controls. Both factors are independently associated with greater disease severity, regardless of adiposity, supporting the value of routine assessment of sleep quality and chronotype to guide personalized management strategies.