End of rarity: the evolving burden of interstitial lung diseases in England – trends from a national population-based cohort study

BACKGROUND: The disease burden from interstitial lung diseases (ILDs) is thought to be increasing globally, but there is a paucity of data on epidemiological trends in non-idiopathic pulmonary fibrosis (IPF) ILD. We calculated incidence, prevalence and mortality rates of all ILD, IPF and non-IPF ILD in England from 2005 to 2022 and investigated trends over time. METHODS: Using linked primary and secondary electronic healthcare records, we used three code-based algorithms to estimate incidence, prevalence and mortality rates of all ILD, IPF and non-IPF ILD subtypes. We additionally stratified our results by sex, age-group and region. Poisson regression was used to investigate changes to trends over time. We used Kaplan-Meier methods to calculate median survival. RESULTS: There were 153 975 incident cases of ILD in either primary or secondary care records. Incidence rates of all ILD, IPF and non-IPF ILD were 30% higher in 2022 compared with 2005, with rates plateauing from 2018 onwards. The prevalence of IPF and non-IPF ILD increased by 6% and 7%, respectively, over the study period. Mortality rates adjusted for age and sex in people with all ILD and non-IPF ILD were similar in 2022 compared with 2005 but in people with IPF it was 15% lower. Median survival of our overall ILD cohort was 5.4 years (IQR 1.88-13.03). CONCLUSIONS: Our population-based study highlights that ILD are no longer rare. Currently, there are 200 000 people living with ILD and 60 000 new cases are diagnosed each year. Healthcare and research funding needs to reflect this growing burden.