Risk of community-acquired pneumonia requiring hospitalization in patients with spondyloarthritis

Aims: To compare the risk of community-acquired pneumonia (CAP) requiring hospitalization in spondyloarthritis (SpA) and non-specific back pain (NSBP), and to identify the risk factors for CAP in SpA. Methods: A total of 2984 patients with SpA from 11 rheumatology centers and 2526 patients with NSBP from orthopedic units were reviewed from the centralized electronic database in Hong Kong. Incidence of CAP requiring hospitalization and demographic data including age, gender, smoking and drinking status, use of sulfasalazine, individual biological-disease modifying anti-rheumatic drugs (DMARDs) used, micro-organisms, other immunosuppressants or immunosuppressive states, use of steroid for more than ½ year, and co-morbidities were identified. Risks of CAP in SpA were compared with those in NSBP using propensity score regression method. Multivariate Cox regression model was used to identify the risk factors in SpA. Results: CAP requiring hospitalization was found in 183 patients with SpA and 138 patients with NSBP. Increased risk for CAP was found in the following groups with SpA: all subgroups (hazard ratio (HR) 2.14, p < 0.001), without use of DMARDs (HR 2.64, p < 0.001), without psoriasis and not taking DMARDs (HR 2.38, p < 0.001). Infliximab (HR2.55, p = 0.04), smoking (HR 1.68, p = 0.003), comorbid psoriasis (HR 1.67, p = 0.003), and use of steroid for more than ½ year (HR 1.94, p = 0.003) were found to associate with CAP after adjustments for traditional risk factors. Conclusion: Risk of CAP is increased in patients with SpA. Our data favor universal influenza and pneumococcal vaccination programs in the population. Rheumatologists should also advise smoking cessation and avoid long term steroid therapy