Impact of preexisting interstitial lung disease on mortality in COVID-19 patients from the early pandemic to the delta variant epidemic: a nationwide population-based study

Abstract

Abstract Background COVID-19 patients with preexisting interstitial lung disease (ILD) were reported to have a high mortality rate; however, this was based on data from the early stages of the pandemic. It is uncertain how their mortality rates have changed with the emergence of new variants of concern as well as the development of COVID-19 vaccines and treatments. It is also unclear whether having ILD still poses a risk factor for mortality. As COVID-19 continues to be a major concern, further research on COVID-19 patients with preexisting ILD is necessary. Methods We extracted data on COVID-19 patients between January 2020–August 2021 from a Japanese nationwide insurance claims database and divided them into those with and without preexisting ILD. We investigated all-cause mortality of COVID-19 patients with preexisting ILD in wild-type-, alpha-, and delta-predominant waves, to determine whether preexisting ILD was associated with increased mortality. Results Of the 937,758 adult COVID-19 patients, 7,333 (0.8%) had preexisting ILD. The proportion of all COVID-19 patients who had preexisting ILD in the wild-type-, alpha-, and delta-predominant waves was 1.2%, 0.8%, and 0.3%, respectively, and their 60-day mortality was 16.0%, 14.6%, and 7.5%, respectively. The 60-day mortality significantly decreased from the alpha-predominant to delta-predominant waves (difference − 7.1%, 95% confidence intervals (CI) − 9.3% to − 4.9%). In multivariable analysis, preexisting ILD was independently associated with increased mortality in all waves with the wild-type-predominant, odds ratio (OR) 2.10, 95% CI 1.91–2.30, the alpha-predominant wave, OR 2.14, 95% CI 1.84–2.50, and the delta-predominant wave, OR 2.10, 95%CI 1.66–2.66. Conclusions All-cause mortality rates for COVID-19 patients with preexisting ILD decreased from the wild-type- to the more recent delta-predominant waves. However, these patients were consistently at higher mortality risk than those without preexisting ILD. We emphasize that careful attention should be given to patients with preexisting ILD despite the change in the COVID-19 environment.