The impact of mild COVID-19 on medium-term respiratory function

J van Heerden; H Strijdom; A Parker; B W Allwood; U Lalla; C J Lombard; C F N Koegelenberg

doi:10.7196/AJTCCM.2024.v30i3.1629

The impact of mild COVID-19 on medium-term respiratory function

Afr J Thorac Crit Care Med. 2024 Oct 14;30(3):e1629. doi: 10.7196/AJTCCM.2024.v30i3.1629. eCollection 2024.

Authors

J van Heerden^{1

2}, H Strijdom², A Parker³, B W Allwood¹, U Lalla^{1

2

3

4

5

6}, C J Lombard^{4

5

6}, C F N Koegelenberg¹

Affiliations

¹ Division of Pulmonology, Department of Medicine, Faculty of Medicine and Health Sciences, Stellenbosch University and Tygerberg Hospital, Cape Town, South Africa.
² Centre for Cardiometabolic Research in Africa, Division of Medical Physiology, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa.
³ Division of Infectious Diseases, Department of Medicine, Faculty of Medicine and Health Sciences, Stellenbosch University and Tygerberg Hospital, Cape Town, South Africa.
⁴ Division of Epidemiology and Biostatistics, Department of Global Health, Stellenbosch University, Cape Town, South Africa.
⁵ Biostatistics Unit, South African Medical Research Council, Cape Town, South Africa.
⁶ Department of Medicine, Faculty of Health Sciences, University of Cape Town, Observatory, South Africa.

Abstract

Background: There is a paucity of evidence on the impact of mild COVID-19 on the respiratory system, particularly in non-healthcare seeking individuals.

Objectives: To investigate the effects of mild COVID-19 on respiratory function and to identify indicators of decreased lung function.

Methods: We conducted a cross-sectional study in 175 non-healthcare-seeking individuals with confirmed acute SARS-CoV-2 infection who did not require hospitalisation. Participants were divided into three groups: those who had pulmonary function tests (PFTs) within 6 months, between 6 and 12 months, and between 12 and 24 months after infection. Each participant underwent spirometry, measurement of the diffusing capacity of the lungs for carbon monoxide (DL_CO ), a 6-minute walking distance test (6MWD) and plethysmography.

Results: The mean age of the participants was 44.3 years, and the mean body mass index (BMI) 32.7 kg/m². Forty-six participants had PFTs within 6 months, 64 between 6 and 12 months, and 65 between 12 and 24 months. Lower than expected DL_CO was the most commonly detected abnormality (57%). Spirometry anomalies were noted in 23%, 10% showing an obstructive impairment and 13% a restrictive impairment, confirmed by a total lung capacity <80%. An increased BMI was the only variable that was significantly and independently linearly associated with lower than predicted (<80%) forced vital capacity, forced expiratory volume in the 1st second, DL_CO and 6MWD.

Conclusion: DL_CO was low in a considerable proportion of non-healthcare-seeking individuals 2 years after mild COVID-19. A high BMI was found to be significantly and independently associated with lower than predicted PFT results and 6MWD.

Study synopsis: What the study adds. We found that pulmonary function, particularly diffusing capacity, was lower than predicted in a significant proportion of non-healthcare-seeking individuals up to 2 years after mild COVID-19. A high body mass index (BMI) was found to be significantly and independently associated with decreased lung function.Implications of the findings. There is a paucity of evidence on the medium-term effects of mild COVID-19 on the respiratory system in non-healthcare-seeking individuals. We investigated the medium-term effects of mild COVID-19 on the respiratory system, showed lower than predicted lung function, and identified one independent predictor, BMI. Even individuals classified as having 'mild' COVID-19 could have medium-term respiratory sequelae.

Keywords: Body mass index; carbon monoxide; diffusion; mild COVID-19; pulmonary function tests.