Incidence of von Willebrand disease in Denmark, 1995-2016: A cohort study

Introduction Information about temporal development of von Willebrand disease (VWD) incidence at a population level is scarce. To our knowledge, no study has described the incidence of VWD at a population level. Aim To estimate overall and annual incidence rates of hospital diagnosed VWD in Denmark between 1995 and 2016 as well as the frequency of hospital treated bleeding episodes before and after VWD diagnosis. Methods A registry-based cohort study that included all Danish patients with a first diagnosis of VWD in Denmark, identified in the Danish National Patient Registry through 1995-2016. Results We identified 1,035 patients with a diagnosis of VWD. The overall incidence rate of VWD in 1995-2016 was 8.6 (95% CI: 8.1-9.2). The annual age-standardized incidence rate per 100 000 person-years varied between 4.1 (95% CI: 2.4-5.9) in 1998 and 16.7 (95% CI: 13.1-20.3) in 2005. A prominent peak in rates appeared from 2002 to 2008. One and five years before VWD diagnosis, 6% and 11.5% of the patients had at least one hospital treated bleeding episode. One and five years after diagnosis, the corresponding percentages were 7.9% and 13.4%. Conclusion These results are the first population-based estimates of VWD incidence. The incidence may be underestimated because asymptomatic individuals may not be diagnosed. The observed peak in incidence from 2002-2008 may be explained by increased medical attention, leading to more patients being diagnosed, rather than an actual increase in VWD incidence. However, overall, we observed no systematic changes in VWD incidence over the study period.