Many 'mild' COVID patients still battling lung damage a year later

By Dr. Sanchari Sinha Dutta, Ph.D.Sep 12 2023Reviewed by Benedette Cuffari, M.Sc.

A recent study published in the journal PLoS ONE reports that patients with severe coronavirus disease 2019 (COVID-19) are at a higher risk of experiencing persistent pulmonary impairments, even 12 months after disease onset.

Study: One-fourth of COVID-19 patients have an impaired pulmonary function after 12 months of disease onset. Image Credit: fizkes / Shutterstock.com

Background

The COVID-19 pandemic, caused by the emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused unprecedented damage to the global healthcare system, with more than 770 million infections and 6.9 million deaths reported worldwide. A significant proportion of COVID-19 patients continue to experience several health complications, including pulmonary impairments, even after complete resolution of the acute infection, collectively referred to as long-COVID.

Reduced carbon monoxide diffusing capacity, together with reduced alveolar volume, is the most prominent pulmonary effect of SARS-CoV-2 infection. This reduction in pulmonary function primarily depends on the disease severity during the acute infection phase.

Previous longitudinal studies have reported improved pulmonary functions in COVID-19 patients between eight and 12 months after disease onset. However, these studies have primarily included severe COVID-19 patients requiring hospitalization.

In the current study, scientists compare pulmonary functions and determinants of pulmonary functions in mild, moderate, and severe COVID-19 patients during a one-year follow-up period after disease onset.

Study design

The current study included both hospitalized and non-hospitalized COVID-19 patients from the RECoVERED cohort study, which is an observational study comprising mild, moderate, and severe COVID-19 patients who are longitudinally examined at regular intervals for various clinical parameters, including pulmonary functions.

A total of 301 RECoVERED cohort study patients who underwent at least one pulmonary test between May 2020 and December 2021 were included in the study. Diffusing capacity for carbon monoxide and breathing patterns were measured to assess the dynamics of pulmonary functions of patients over a period of 12 months after disease onset.

Data on sociodemographic features, clinical characteristics, symptoms, and health-related quality of life were collected through patient interviews and medical records. These parameters were analyzed to identify the determinants of impaired pulmonary functions.

Pulmonary function after COVID-19

Among 301 patients included in the study, 30%, 44%, and 26% experienced mild, moderate, and severe COVID-19, respectively. About 47% of the study cohort were hospitalized, 13% of whom were admitted to the intensive care unit (ICU).

Pulmonary functions of the patients were measured at one, six, and 12 months after disease onset. At the one-month time point, a reduced diffusion capacity was observed in 26%, 23%, and 74% of mild, moderate, and severe COVID-19 patients, respectively.

No significant improvement in diffusion capacity was observed in patients with mild infection during the study period. In contrast, moderately and severely infected patients exhibited continuous improvements in diffusion capacity until 12 months after disease onset.

The analysis of pulmonary function determinants revealed that older age, female sex, higher number of comorbidities, and disease severity during acute infection were significantly associated with slower improvement in diffusion capacity over time.

A significantly reduced diffusion capacity was observed in 11%, 22%, and 48% of mild, moderate, and severe COVID-19 patients after 12 months of disease onset, respectively. After adjusting for age and sex, severe COVID-19 and the presence of any comorbidity were identified as significant risk factors for persistently reduced diffusion capacity.

Health-related quality of life

Health-related quality of life, including functional status, well-being, and overall health evaluation, was measured at one and 12 months. The age- and sex-adjusted findings revealed that patients with reduced diffusion capacity after one month of disease onset exhibited significantly lower physical functioning and general health.

After 12 months of disease onset, no significant difference in health-related quality of life was observed between patients with and without impaired pulmonary functions.

Study significance

A significantly higher prevalence of persistently impaired pulmonary function was observed in patients with moderate or severe COVID-19 as compared to patients who have recovered from mild COVID-19. Nevertheless, a gradual improvement in pulmonary functions over a period of 12 months was observed in severe COVID-19 patients. 

These findings emphasize the importance of continuously monitoring patients' health who have recovered from severe COVID-19 to effectively manage their long COVID symptoms.