Metabolic Syndrome Is Independently Associated with Pain Severity in Psoriatic Arthritis

Objective: Pain in psoriatic arthritis (PsA) is multifactorial and may persist despite apparently controlled inflammatory activity. Metabolic syndrome (MetS), a frequent comorbidity in PsA, could contribute to increased pain burden beyond inflammatory disease activity. The objective was to investigate the association between MetS and pain burden in PsA, focusing on pain intensity (BPI severity; primary outcome) and pain-related functional impact (BPI interference; secondary outcome), and to assess whether these associations are independent of disease activity (DAPSA) and fibromyalgia. Methods: PSABRAIN is a cross-sectional, monocentric study including consecutive adult patients with PsA (CASPAR criteria). MetS was defined according to modified ATP III criteria. Pain outcomes were assessed using the Brief Pain Inventory (BPI) severity and interference subscales. Group comparisons (MetS vs. no MetS) were performed using appropriate parametric/non-parametric tests. Univariable and multivariable linear regression models were fitted for BPI severity and BPI interference. Multivariable models were adjusted for age, sex, disease duration, fibromyalgia, and DAPSA. Robustness analyses replaced MetS with BMI (continuous), obesity, and overweight. Results: A total of 187 PsA patients were included (44 with MetS; 143 without). MetS patients were older (median 62 vs. 57 years, p = 0.0017), had higher BMI (median 30.1 vs. 25.5 kg/m², p < 0.001) and a higher prevalence of obesity (56.8% vs. 15.4%, p < 0.001), while DAPSA did not differ between groups (p = 0.819). MetS patients reported higher BPI severity (median 5.75 vs. 4.5, p = 0.038) and BPI interference (median 6.86 vs. 5.5, p = 0.044). In univariable regression, MetS was associated with higher BPI severity (β = 0.93, 95% CI 0.08 to 1.77; p = 0.032) but not with BPI interference (β = 0.81, 95% CI -0.13 to 1.75; p = 0.091). In adjusted models, MetS remained independently associated with BPI severity (β = 0.99, 95% CI 0.23 to 1.75; p = 0.011), whereas its association with BPI interference was not significant (β = 0.69, 95% CI -0.20 to 1.57; p = 0.126). In alternative models, BMI and obesity were independently associated with both outcomes (BPI severity: BMI β = 0.097/kg/m², p = 0.004; obesity β = 0.91, p = 0.010; BPI interference: BMI β = 0.095/kg/m², p = 0.015; obesity β = 1.22, p = 0.003). Conclusions: In PsA, MetS is independently associated with higher pain severity but not with pain interference after adjustment for disease activity and fibromyalgia. Adiposity measures show consistent independent associations, particularly with pain interference, supporting the relevance of metabolic and weight-related factors in the multidimensional assessment of pain in PsA.