Chronic Lung Disease as a Risk Factor for Long COVID in Patients Diagnosed with COVID-19: A Retrospective Cohort Study
Background: Patients with coronavirus disease 2019 (COVID-19) experience a wide range of ongoing symptoms after the acute phase of SARS-CoV-2 infection. Chronic lung disease has been shown to be a potential risk factor for persistent post-COVID conditions (PCC or long COVID).
Objective: This study aimed to examine the relationship between chronic lung disease before COVID infection and the incidence of long COVID.
Method: We conducted a retrospective cohort study to evaluate the association between chronic lung disease and the incidence of long COVID during a 6-month follow-up period after the acute phase of the infection. Data were sourced from the National COVID Cohort Collaborative (N3C) Data Enclave. Patients included were adults (18-65 years of age), 1) who were confirmed COVID positive during three consecutive SARS-CoV-2 variant dominance periods (Pre-Delta wave from December 29, 2020 to June 14, 2021; Delta wave from June 15, 2021 to November 29, 2021; Omicron wave from November 30, 2021 to June 15, 2022); 2) who completed the 6-month follow-up after acute phase; 3) who were diagnosed with long COVID within 6 months after acute phase but were lost to follow up thereafter. Otherwise, patients who were lost to follow up before the end of follow-up period were excluded. Patients who died from COVID during acute phase were also excluded. We used multivariate logistic regression to evaluate the association between long COVID and chronic lung disease as well as other risk factors. Sensitivity analysis was conducted by removing those who were lost to follow up after long COVID diagnosis.
Results: 970,707 patients were included in the study cohort. The overall incidence of long COVID was 1.2%. Chronic lung disease was significantly associated with long COVID (adjusted OR:1.4, 95% CI: 1.34 to 1.47). Reinfection after COVID increased the odds for long COVID by 17% (adjusted OR 1.17, 95% CI: 1.01 to 1.34) among patients with chronic lung disease, but it had no effect on long COVID risk among those without chronic lung disease (adjusted OR: 1.02, 95% CI: 0.93 to 1.12). Cardiomyopathy was also associated with long COVID among patients with chronic lung disease (adjusted OR 1.2, 95% CI: 1.01 to 1.43). Female sex and age of 40-65 years were related to higher odds for long COVID in both subgroups. Sensitivity analysis provided consistent results after removing the patients who were lost to follow up after being diagnosed with long COVID.
Conclusion: Underlying chronic lung disease is associated with a higher risk for long COVID during 6 months after acute phase of the infection. Precautions should be taken in this population, especially females, those at the age of 40 to 65 years, those with reinfections post COVID or cardiomyopathy.