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

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

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

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.

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.

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.

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.