Comparisons of Comorbidities in Patients with Ankylosing Spondylitis and Psoriatic Arthritis and their Influence on Psoriatic Arthritis Disease Activity: Results of a Multicentre Longitudinal Study

Abstract Objectives: To compare the presence of psycho-affective disorders and obesity-associated factors between ankylosing spondylitis (AS) and psoriatic arthritis (PsA) patients and to corelate these comorbidities with PsA disease activity.Methods: This prospective observational longitudinal study included 216 PsA patients and 114 AS patients. Anxiety and depression were compared between both patient groups using the Hospital Anxiety and Depression Scale (HADS) questionnaire. We compared the waist/hip ratio, body mass index (BMI) and laboratory variables including apolipoprotein A, apolipoprotein B, lipoprotein A, the ApoB/ApoA ratio, peptide C, insulin, resistance to insulin (HOMA-IR) and leptin. PsA activity was evaluated by the Disease Activity Index for Psoriatic Arthritis (DAPSA) score every 4 months for a year. Patients were divided into two groups: those with moderate or high activity and those with low activity or remission. We compared anxiety-, depression- and obesity-related factors between these two groups.Results: There were no differences in baseline characteristics between AS and PsA patients. Among the studied factors, only serum leptin was significantly higher in PsA patients than in AS patients (18.49±19.01 vs 11.5±10.05, p<0.01). Initial serum leptin, obesity and depressive behaviour were poor prognostic factors for persistent low disease activity. The leptin level was correlated with the visual analogue scale (VAS) pain score (R=0.21, p<0.01), VAS activity score (R=0.26, p<0.01), swollen joint count (SJC) (R=0.23, p<0.01) and tender joint count (TJC) (R=0.26, p<0.01).Conclusion: Obesity alone or concurrent with increased leptin secretion and depression may influence persistent PsA activity. Leptin levels differentiated PsA patients from AS patients.