Incidence and prevalence of asthma, chronic obstructive pulmonary disease and interstitial lung disease between 2004 and 2023: harmonised analyses of longitudinal cohorts across England, Wales, South-East Scotland and Northern Ireland

Abstract

Background: We describe the epidemiology of asthma, chronic obstructive pulmonary disease (COPD) and interstitial lung disease (ILD) from 2004 to 2023 in England, Wales, Scotland and Northern Ireland (NI) using a harmonised approach.

Methods: Data from the National Health Service England (NHSE), Clinical Practice Research Datalink Aurum in England, Secure Anonymised Information Linkage Databank in Wales, DataLoch in South-East Scotland and the Honest Broker Service in NI were used. A harmonised approach to COPD, asthma and ILD case definitions, study designs and study populations across the four nations was performed. Age-sex-standardised incidence rates and point prevalence were calculated between 2004 and 2023 depending on data availability. Logistic and negative binomial regression compared incidence and prevalence rates between the start and end of each study period. Linear extrapolation projected incidence rates between 2020 and 2023 to illustrate how observed and projected rates differed.

Results: Incidence rates were lower in 2019 versus 2005 for asthma (England: incidence rate ratio 0.89, 95% CI 0.88 to 0.90; Wales: 0.66, 0.65 to 0.68; Scotland: 0.67, 0.64 to 0.71; NI: 0.84, 0.81 to 0.86), COPD (England: 0.83, 0.82 to 0.85; Wales: 0.67, 0.65 to 0.69) and higher for ILD (England: 3.27, 3.05 to 3.50; Wales: 1.39, 1.27 to 1.53; Scotland: 1.63, 1.36 to 1.95; NI: 3.03, 2.47 to 3.72). In NHSE, the incidence of asthma was similar in June 2023 versus November 2019, but lower for COPD and higher for ILD. Prevalence of asthma in 2019 in England, Wales, Scotland and NI was 9.7%, 15.9%, 13.2% and 7.0%, respectively, for COPD 4.5%, 5.1%, 4.4% and 3.0%, and for ILD 0.4%, 0.5%, 0.6% and 0.3%. Projected incidence rates were 2.8, 3.4 and 1.8 times lower for asthma, COPD and ILD compared with observed rates at the height of the pandemic.

Interpretation: Asthma, COPD and ILD affect over 10 million people across the four nations, and a substantial number of diagnoses were missed during the pandemic.

Keywords: Asthma Epidemiology; COPD epidemiology; Interstitial Fibrosis.

Figure 1. Age and sex adjusted incidence rate of asthma, COPD and ILD. Estimates illustrate incidence rates of asthma, COPD and ILD per 1000 person-years and 95% CIs calculated separately at each time point for England, Wales and Scotland. Yearly incidence rates were calculated for the years 2004 up until the end of 2020 for CPRD, SAIL and DataLoch, monthly incidence rates were calculated from November 2019 up until June 2023 for NHSE and 3-monthly incidence rates were calculated from January 2020 up until March 2023. Yearly incidence was calculated for Northern Ireland. COPD, chronic obstructive pulmonary disease; CPRD, Clinical Practice Research Datalink; ILD, interstitial lung disease; NHSE, National Health Service England; SAIL, Secure Anonymised Information Linkage.

Figure 2. Crude incidence rate ratios (IRR) or incidence ratio (IR) of (A) asthma, (B) COPD and (C) ILD in 2019 versus 2005 for England, Wales, South-East Scotland and Northern Ireland and in June 2023 versus November 2019 for NHSE. Estimates illustrate IRR and 95% CIs for England, Wales and Scotland and IR for Northern Ireland. COPD, chronic obstructive pulmonary disease; CPRD, Clinical Practice Research Datalink; ILD, interstitial lung disease; IR, incidence ratio; IRR, incidence rate ratio; NHSE, National Health Service England.

Figure 3. Point prevalence of asthma, COPD and ILD. Estimates illustrate point prevalence per 100 individuals and 95% CIs calculated separately at each time point. Point prevalence was calculated on the first of July of each year between 2004 and 2019 for England and Wales and between 2004 and 2022 for Lothian, Scotland and Northern Ireland. COPD, chronic obstructive pulmonary disease; CPRD, Clinical Practice Research Datalink; ILD, interstitial lung disease; SAIL, Secure Anonymised Information Linkage.

Figure 4. Crude odds ratios (OR) for the odds of (A) asthma, (B) COPD and (C) ILD in 2019 versus 2005 in England, Wales and South-East Scotland and 2019 versus 2011 in Northern Ireland. Estimates illustrate OR and 95% CIs. COPD, chronic obstructive pulmonary disease; ILD, interstitial lung disease.