Polyarteritis nodosa: decreasing incidence in Poland

Introduction: There are many studies on the epidemiology of the orphan disease polyarteritis nodosa (PAN) in European countries. The use of a hospital morbidity database is an important element of epidemiological analysis. The study is the first such analysis in Poland and may provide an opportunity to compare the data in a European context. Material and methods: We conducted a retrospective, population-based study using hospital discharge records with a PAN diagnosis. PAN incidence was estimated based on data from a Polish hospital morbidity study carried out by the National Institute of Public Health. Data on all inpatients discharged from non-psychiatric hospitals in Poland were collected between 2008 and 2013. We identified 557 patients with first-time hospitalizations for PAN. Results: The sample consisted of 202 (36.3%) males and 355 (63.7%) females. The median and mean age was 53 and 50 years, respectively. The average annual incidence of PAN in Poland was estimated to be 2.4 per million. PAN incidence decreased significantly over time in Poland between 2008 and 2013 (3.3 per million vs 1.9 per million, p < 0.001) and it may be associated with a decrease in hepatitis B incidence observed in Poland. Conclusions: Incidence of PAN in Poland was estimated to be 2.4 per million and was comparable to the incidence found in other European countries. PAN incidence decreased during 2008-2013. The decrease in PAN incidence may be related to environmental, infectious (hepatitis B) or other unknown factors. Future research is needed to identify the cause of the decrease and potential triggers of the disease.