Incidence, prevalence and mortality of idiopathic pulmonary fibrosis in England from 2008 to 2018: a cohort study.

Background: Owing to discrepancies in methodologies and how idiopathic pulmonary fibrosis (IPF) is diagnosed it is challenging to establish a consistent understanding of the disease burden In the UK, over 10 years ago, the incidence and prevalence of IPF were reported as 2.8-8.7 per 100 000 person-years (from 2000 to 2012) and 39 per 100 000 persons (in 2012), respectively. Here, we estimated the incidence and prevalence of IPF in England from 2008 to 2018 and investigated IPF mortality.

Methods: Using Clinical Practice Research Datalink Aurum and Hospital Episode Statistics (HES) linked datasets, we estimated incidence and prevalence using four validated diagnostic-code-based algorithms. Using the registered number of deaths (from Office of National Statistics) with the underlying cause being recorded as IPF, we estimated IPF mortality for the same period.

Results: Using Aurum-based definitions, incidence increased over time by 100% for Aurum narrow (3-6.1 per 100 000 person-years) and by 25% for Aurum broad (22.4-28.6 per 100 000 person-years). However, using HES-based definitions showed a decrease in incidence over the same period and lay between the two extremes derived for Aurum-based definition. IPF mortality in 2018 was 7.9 per 100 000 person-years and increased by 53% between 2008 and 2018.

Interpretation: When using best-case definitions, incidence rose throughout the study period. Scaling this to England's population (2018), our best estimate would be in the range of 8000-9000 new cases per year which is higher than previously reported estimates (5000-6000). This increased burden in the new cases of IPF each year impacts future health service planning and resource allocation.