3-month, 6-month, 9-month, and 12-month respiratory outcomes in patients following COVID-19-related hospitalisation: a prospective study

Abstract

Background: The consequences of COVID-19 in those who recover from acute infection requiring hospitalisation have yet to be clearly defined. We aimed to describe the temporal trends in respiratory outcomes over 12 months in patients hospitalised for severe COVID-19 and to investigate the associated risk factors.

Methods: In this prospective, longitudinal, cohort study, patients admitted to hospital for severe COVID-19 who did not require mechanical ventilation were prospectively followed up at 3 months, 6 months, 9 months, and 12 months after discharge from Renmin Hospital of Wuhan University, Wuhan, China. Patients with a history of hypertension; diabetes; cardiovascular disease; cancer; and chronic lung disease, including asthma or chronic obstructive pulmonary disease; or a history of smoking documented at time of hospital admission were excluded at time of electronic case-note review. Patients who required intubation and mechanical ventilation were excluded given the potential for the consequences of mechanical ventilation itself to influence the factors under investigation. During the follow-up visits, patients were interviewed and underwent physical examination, routine blood test, pulmonary function tests (ie, diffusing capacity of the lungs for carbon monoxide [DLCO]; forced expiratory flow between 25% and 75% of forced vital capacity [FVC]; functional residual capacity; FVC; FEV₁; residual volume; total lung capacity; and vital capacity), chest high-resolution CT (HRCT), and 6-min walk distance test, as well as assessment using a modified Medical Research Council dyspnoea scale (mMRC).

Findings: Between Feb 1, and March 31, 2020, of 135 eligible patients, 83 (61%) patients participated in this study. The median age of participants was 60 years (IQR 52-66). Temporal improvement in pulmonary physiology and exercise capacity was observed in most patients; however, persistent physiological and radiographic abnormalities remained in some patients with COVID-19 at 12 months after discharge. We found a significant reduction in DLCO over the study period, with a median of 77% of predicted (IQR 67-87) at 3 months, 76% of predicted (68-90) at 6 months, and 88% of predicted (78-101) at 12 months after discharge. At 12 months after discharge, radiological changes persisted in 20 (24%) patients. Multivariate logistic regression showed increasing odds of impaired DLCO associated with female sex (odds ratio 8·61 [95% CI 2·83-26·2; p=0·0002) and radiological abnormalities were associated with peak HRCT pneumonia scores during hospitalisation (1·36 [1·13-1·62]; p=0·0009).

Interpretation: In most patients who recovered from severe COVID-19, dyspnoea scores and exercise capacity improved over time; however, in a subgroup of patients at 12 months we found evidence of persistent physiological and radiographic change. A unified pathway for the respiratory follow-up of patients with COVID-19 is required.

Funding: National Natural Science Foundation of China, UK Medical Research Council, and National Institute for Health Research Southampton Biomedical Research Centre.

Translation: For the Chinese translation of the abstract see Supplementary Materials section.

Figure 1

Trial profile HRCT=high-resolution CT. 6MWD=6-min walk distance. mMRC=modified Medical Research Council dyspnoea scale. *Because of changes in local guidance, pulmonary function tests were precluded at 9 months after discharge.

Figure 2

Temporal changes in pulmonary function following severe COVID-19-related hospitalisation Graphs show temporal changes in DLCO (A) or FVC (B) at 3 months, 6 months, and 12 months after discharge in patients with severe COVID-19. Data are median (IQR). Figure shows n (%) of patients with abnormal DLCO or FVC. Horizontal dotted lines indicate the normal cutoff of 80%. DLCO=diffusing capacity of the lungs for carbon monoxide. FVC=forced vital capacity.

Figure 3

Effect of severe COVID-19 on follow-up 6MWD test and mMRC score Panel A shows temporal changes in 6MWD at 3 months, 6 months, 9 months, and 12 months after discharge. Data are median (IQR). Panel B shows the distributions of mMRC scores at 3 months, 6 months, 9 months, and 12 months after discharge. Figure shows n (%) of patients without dyspnoea. 6MWD=6-minute walking distance. mMRC=modified Medical Research Council dyspnoea scale.