Clinical and Psychosocial Predictors of Physical Activity in Systemic Lupus Erythematosus: A Multicentre Cross-Sectional Study

<b>Background/Objectives</b>: Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterised by musculoskeletal manifestations such as myopathies, arthritis, and arthralgia. Physical activity may improve patients' quality of life and overall wellbeing. This study aimed to evaluate physical activity levels in patients with SLE and identify how clinical, psychosocial, and sociodemographic factors influence these levels. <b>Methods</b>: A multicentre cross-sectional study was conducted including 64 patients with SLE. Clinical variables were obtained from medical records, and patient-reported outcomes were collected at the time of the survey. Physical activity was assessed using the International Physical Activity Questionnaire (IPAQ-SF). Independent variables included fatigue (FAS), quality of life (SF-36), sleep (PSQI), depression (BDI-II), anxiety (HARS), age, disease factors (activity, duration, damage), sex, smoking, and comorbidities. <b>Results</b>: Significant associations were found between physical activity levels and smoking status (χ² = 11.88; <i>p</i> = 0.003), sleep quality (χ² = 6.81; <i>p</i> = 0.03), and anxiety (χ² = 18.39; <i>p</i> = 0.001). In multivariable analyses, poor sleep (PSQI > 5) (OR = 14.40; 95% CI: 2.50-82.99), higher anxiety (HARS; per point OR = 1.12; 95% CI: 1.05-1.20), and higher SF-36 Physical Component Summary (PCS) scores (per point OR = 1.29; 95% CI: 1.15-1.45) were associated with being in a higher physical activity category. Given the counterintuitive direction for sleep and the limited model fit, these results should be interpreted cautiously. <b>Conclusions</b>: In patients with SLE, physical activity was associated with sleep disturbances, anxiety, and perceived physical health. These findings underscore the need to integrate psychosocial and behavioural factors into multidisciplinary strategies promoting physical activity in lupus care and provide a rationale for future longitudinal and interventional studies to validate and extend these associations.