The Epidemiology of Alpha-1 Antitrypsin Deficiency in Norway.

Background: Alpha-1 antitrypsin deficiency (AATD) is a genetic condition characterized by insufficient levels of alpha-1 antitrypsin and elevated risk of lung and liver disease. We aimed to estimate the prevalence and incidence of diagnosed AATD (dAATD) in Norway, and mortality after dAATD. Methods: A nationwide cohort of individuals diagnosed with AATD between 2008 and 2019 was identified from the Norwegian Patient Registry. Prevalence and incidence rates were standardized to the Norwegian population as of December 31, 2019. Mortality rate ratios (MRRs) were calculated to compare mortality between patients with dAATD and a randomly sampled, 10:1 matched general population comparison cohort. Results: A total of 827 patients with dAATD were identified during the study period. The prevalence of dAATD in Norway at the end of 2019 was 10.7 per 100,000 people (95% confidence interval [CI]: 9.8-11.5), and the incidence rate was 1.4 per 100,000 person-years (95% CI: 1.3-1.5). Mortality among patients with dAATD was markedly elevated, with an MRR of 6.2 (95% CI: 5.3-7.2) with respect to the general population comparison cohort. Among patients with AATD, 26.8% had an emphysema diagnosis, 12.5% had an asthma diagnosis, and 6.4% had a liver disease diagnosis. Conclusion: This study provides the first national estimates of dAATD frequency and mortality in Norway. The mortality for patients with dAATD was found to be markedly elevated compared with their age and sex matched peers, indicating a substantial disease burden and suggesting the need for improved diagnosis and earlier therapeutic interventions.