Lung function at 1-year follow-up in patients with persistent dyspnea after mild COVID-19 – comparisons with moderate and critical COVID-19

Aim: To assess lung function in patients with persistent dyspnea 1 year after mild coronavirus disease 2019 (COVID-19) and compare with those hospitalized with moderate or critical COVID-19. Methods: Adults with confirmed severe acute respiratory syndrome coronavirus-2 infection with mild COVID-19 and persistent dyspnea (n = 18) or with moderate (n = 34) or critical COVID-19 (n = 19) were followed up 11–13 months after initial infection. Inclusion criteria were age < 65 years, no smoking history, and no preexisting respiratory diseases. Sociodemographic and clinical data were collected, and patients underwent spirometry and measurement of diffusing capacity for carbon monoxide (DLCO). Results: The non-hospitalized patients were significantly younger and more often female compared with those in the moderate and critical groups (P = 0.002 and P < 0.001, respectively). No significant differences in comorbidities or body mass index (BMI) were noted between severity groups. An obstructive spirometry pattern (ratio of forced expiratory volume during the first exhalation second to forced vital capacity under the lower limit of normal (LLN)) was found in 5.6, 5.9, and 5.3% of patients in the mild, moderate, and critical groups, respectively (P = 0.995). Abnormal DLCO (< LLN) rates were seen in 5.6, 16.7, and 47.4% in the mild, moderate, and critical groups, respectively (P = 0.018). DLCO, expressed as a z-score, was significantly lower in the critical group compared with the mild group after adjustment for age, sex, and BMI. Conclusion: Only a few subjects with mild COVID-19 and persistent dyspnea had abnormal lung function 1 year after initial infection, assessed based on spirometry and DLCO measurements. An obstructive spirometry pattern at 1-year follow-up was uncommon even in patients with moderate or critical COVID-19. Impaired DLCO was more common in patients with critical COVID-19.