IgA Nephropathy and the Risk of Primary Infections: A Swedish population-based cohort study

IgA nephropathy is the most common primary kidney disease in the world and has a highly variable clinical presentation. While studies have indicated a link between glomerular disease and infections, large-scale studies on IgA nephropathy are missing. In our study, IgA nephropathy was defined as having a kidney biopsy record 1997-2011 in Sweden. Each IgA nephropathy patient was matched with five reference individuals based on age, sex, calendar year, and county of residence. We excluded individuals with earlier organ transplants, HIV, immunodeficiency, or end-stage kidney disease. Linear and Cox regressions, adjusted for age, sex, education and diabetes, were performed to analyze total infections and antimicrobial treatments in both patients and reference individuals. Sibling analyses were also performed. The linear regression analysis revealed a significant association between IgA nephropathy and the overall frequency of infections compared to the general population (β=0.44; 95%CI: 0.35-0.53) and siblings (β=0.36; 95%CI:0.23-0.49). Similarly, antimicrobial prescriptions, especially antibiotics, were more common in IgA nephropathy compared to the general population and to siblings. Cox regression showed an elevated risk of any infection (adjusted hazard ratio (HR)=2.00; 95%CI 1.84-2.18) and sepsis (aHR=3.18; 95%CI 2.17-4.65) corresponding to one extra case of sepsis per 63 patients followed for 10 years. The strongest associations were seen for urinary tract infections; ear, nose, and throat infections; musculoskeletal and gastrointestinal infections. Conclusively, our study demonstrates an increased prevalence of infections and antibiotic prescriptions in IgA nephropathy patients. The increased risk of sepsis warrants clinical awareness and prevention.