Lung abnormalities persist in 36% of individuals 3 years after COVID-19 hospitalization

Key takeaways:

• Six-minute walk distance significantly improved between the 6-month and 3-year follow-ups.
• Researchers observed poorer outcomes among those with residual lung abnormalities vs. complete resolution at 3 years.

Three years after hospital discharge for COVID-19, 36% of individuals still had residual lung abnormalities, according to results published in European Respiratory Journal.

“This study illustrates ongoing improvement in respiratory outcomes up to 3 years after COVID-19,” Xiaoyu Han, PhD, of the department of radiology at Union Hospital of Tongji Medical College, and colleagues wrote. “However, a significant proportion of patients, particularly those with severe initial infections, continue to exhibit radiological lung abnormalities and abnormal pulmonary function.”

In a longitudinal, prospective cohort study, Han and colleagues assessed 728 individuals (median age, 61 years; 57% men) who survived a COVID-19 infection and had residual lung abnormalities upon discharge to look for changes in radiological abnormalities and lung function 3 years after hospital discharge.

Notably, Han and colleagues previously found that 39% of patients who suffered a COVID-19 infection had interstitial lung abnormalities 2 years following the illness.

Researchers evaluated patients’ chest CT scans, pulmonary function tests, 6-minute walk distance (6MWD) and responses to symptom questionnaires at four different time points: 6 months, 12 months, 2 years and 3 years after discharge.

Within the total cohort, most individuals fell under severity scale 4 (n = 490), meaning they needed supplemental oxygen via nasal cannula/mask while hospitalized. The remaining individuals either belonged to the highest severity scale group (5 to 6) that needed high-flow nasal cannula, non-invasive mechanical ventilation or invasive mechanical ventilation while hospitalized (n = 131) or the lowest severity scale group (3) that did not need supplemental oxygen while hospitalized (n = 107).

At the 3-year mark, the proportion of individuals with residual lung abnormalities was 36%, which was a significant reduction from 46% at the 6-month mark (P < .001).

In each disease severity group, non-fibrotic changes went down from 6 months to 3 years after discharge. Fibrotic-like changes appeared primarily in the severity scale 5-6 group and did not change between 6 months and 3 years.

6MWD also significantly improved between the 6-month and 3-year follow-ups from 496 m to 510 m (P = .002). When split up by severity scale, this outcome was true in each group.

In terms of lung function, significantly fewer individuals had a diffusing capacity of the lung for carbon monoxide (DLCO) less than 80% predicted at 3 years vs. 6 months after discharge (38% vs. 49%; P = .001). Similar to above, this pattern was found in each severity scale group.

Although not significant, fewer individuals reported respiratory symptoms at 3 years vs. 6 months following discharge (22% vs. 27%). When grouped by severity scale, this outcome was true for those in groups 3 and 4.

When divided based on residual lung abnormalities vs. complete resolution at 3 years, researchers observed poorer outcomes among those with residual lung abnormalities. A greater proportion of patients with abnormalities had respiratory symptoms (32% vs. 16%; P < .001) and abnormal DLCO (57% vs. 27%; P < .001), as well as shorter 6MWD (494 m vs. 510 m; P = .003).

Researchers also carried out another analysis to see how these variables differed between COVID-19 survivors at 3 years and matched non-COVID-19 controls (n = 644).

DLCO impairment appeared more frequently in COVID-19 survivors vs. non-COVID-19 controls (38% vs. 17%; P < .001). Additionally, 23% of COVID-19 survivors reported a respiratory symptom, whereas only 2.2% of controls reported a minimum of one symptom (P < .001).

“Residual lung abnormalities, particularly the fibrotic-like changes on CT, are associated with persistent respiratory symptoms and abnormal pulmonary function, and should be considered in long-term management strategies for COVID-19 survivors,” Han and colleagues wrote.