Ankylosing spondylitis (AS) is an immune-mediated chronic inflammatory disease that primarily affects young adults, imposing a significant burden on physical function and social participation. While tumor necrosis factor inhibitors (TNFi) have significantly improved AS outcomes, evidence is primarily derived from randomized controlled trials (RCTs). Real-world data from China remains insufficient. This study established a real-world cohort of Chinese AS patients treated with TNFi to evaluate clinical efficacy, regional differences, and the impact of social determinants on treatment outcomes.

This prospective, multicenter, real-world cohort study enrolled AS patients diagnosed at 337 designated hospitals across 29 provinces in China between January and March 2024. Data on demographics, socioeconomic factors, clinical symptoms, comorbidities, disease activity, physical function, and health-related quality of life (HRQoL) were collected via electronic medical records. Patients were categorized into rural and urban groups based on household registration. All patients received TNFi treatment. Clinical responses (ASAS20/40), disease activity (ASDAS, BASDAI), physical function (BASFI), and HRQoL were assessed at 1, 3, and 6 months post-treatment. Generalized linear mixed models (GLMM) were used to analyze the impact of socioeconomic factors and HRQoL on ASAS20/40 responses.

A total of 3,156 patients were enrolled, including 1,434 (45.44%) urban and 1,722 (54.56%) rural patients. The cohort was predominantly male (71.36%), with an HLA-B27 positivity rate of 87.99%. The mean age at onset was 32.14 ± 10.59 years, and the diagnostic delay was 3.12 ± 4.17 years. Rural patients exhibited higher prevalences of HLA-B27 positivity, family history, smoking, and alcohol consumption, as well as an older age at diagnosis and longer disease duration. Lower back pain and morning stiffness were the most common initial symptoms. Rural patients exhibited a higher burden of peripheral arthritis, dactylitis, uveitis, and inflammatory bowel disease. At baseline, the mean ASDAS was 3.26 ± 1.09, indicating high or very high disease activity in most patients. Following TNFi treatment, ASAS20 response rates at 1, 3, and 6 months were 33.42%, 54.21%, and 69.53%, respectively; ASAS40 rates were 11.95%, 24.81%, and 45.27%, which were slightly lower than reported RCT data. Urban patients showed faster and greater improvements in ASDAS, BASDAI, and BASFI compared to rural patients. GLMM analysis identified rural residence, medical insurance, and unemployment as independent predictors of lower ASAS response, while Han ethnicity and having children were associated with higher response rates.

In this real-world cohort, TNFi treatment showed substantial clinical benefits, although response rates remained marginally lower than those observed in RCTs. Significant disparities exist between urban and rural patients regarding disease characteristics, symptom burden, and treatment benefits, with rural patients showing poorer disease control and quality of life. Social determinants and HRQoL are critical factors influencing AS outcomes, suggesting that clinical management should integrate social, psychological, and individual dimensions.