Rheumatoid arthritis epidemiology: a nationwide study in Poland.

To assess the incidence and prevalence of rheumatoid arthritis (RA) in Poland for the period 2013-2021, total and dependent on gender, age, region and serological status. Information on reported National Health Fund (NHF) health services and reimbursed prescriptions were used, defining an RA patient as a person who had at least two visits in different quarters with ICD-10 code M05 or M06 and at the same time filled at least one reimbursed prescription for a drug whose active substance is methotrexate, sulfasalazine, leflunomide or was treated with biologic disease-modifying anti-rheumatic drugs (bDMRDs) or targeted synthetic DMARDs (tsDMARDs) as part of a drug program financed by the National Health Fund. The nationwide standardised incidence rate of RA in 2021 was 29 persons per 100,000 population (18 per 100,000 population of seropositive vs. 11 per 100,000 population of seronegative RA). The prevalence of RA in Poland in 2021 was 689.0 people per 100,000 population, a total of 0.7% (1.1% in women and 0.3% in men). The incidence of seronegative RA was approximately 38%. The majority of new RA diagnoses were in the sixth and seventh decades of life, irrespective of patients' gender. The results allow RA to be classified as a disease with a significant social impact. A trend of later onset of RA has been observed, which requires special consideration of the needs of patients over 55 years of age.