Lung-function trajectories in COVID-19 survivors after discharge: A two-year longitudinal cohort study

Background Data on the long-term trajectories of lung function are scarce in COVID-19 survivors.Methods We re-analyzed the data from a prospective longitudinal cohort follow-up study of COVID-19 survi-vors over 2 years after infection. All participants were divided into scale 3, scale 4 and scale 5-6 groups accord-ing to seven-category ordinal scale. The changes of pulmonary function tests (PFTs), the Modified Medical Research Council (mMRC) Dyspnea Scale, 6-min walking test health-related quality of life (HRQoL) across the three serial follow-up visits were evaluated, and compared among three groups. We performed liner regression to determine potential factors that were associated with changes of PFTs and distance walked in 6 minutes (6MWD).Findings In this study, 288 participants generally presented an improvement of PFTs parameters from 6 months to 1 year after infection. The scale 5-6 group displayed a significantly higher increase of PFTs compared with scale 3 and scale 4 groups (all p<0.0167), and corticosteroids therapy was identified as a protective factor for the PFTs improvement with a correlation coefficient of 2.730 (0.215-5.246) for forced vital capacity (FVC), 2.909 (0.383 -5.436) for total lung capacity (TLC), and 3.299 (0.211-6.387) for diffusion capacity for carbon monoxide (DLco), respectively. From 1-year to 2-year follow-up, the PFTs parameters generally decreased, which was not observed to be associated with changes of 6MWD and HRQoL. Dyspnea (mMRC >= 1) generally decreased over time (23.3% [61/ 262] for 6-month, 27.9% [67/240] for 1-year, 13.4% [35/261] for 2-year), and 6MWD increased continuously (500.0 m vs 505.0 m vs 525.0 m).Interpretation Corticosteroids therapy during hospitalization was a protective factor for PFTs improvement from 6 months to 1 year. The relatively fast decline trend of PFTs from 1 year to 2 years needs to be paid attention and fur-ther validated in the future follow-up study.

Automated summary

This study found that lung function in COVID-19 survivors improved from 6 months to 1 year after infection, but declined from 1 year to 2 years. Corticosteroid therapy was identified as a protective factor for lung function improvement during the first year.