# Pulmonary function in non-hospitalized adults and children after mild COVID-19: a single-centre prospective cohort study

## TL;DR

This study finds that mild COVID-19 can lead to lasting lung issues, especially in adults, even when hospitalization isn't needed.

## Contribution

The study provides new insights into long-term pulmonary effects of mild SARS-CoV-2 infection in non-hospitalized individuals.

## Key findings

- About half of adults and 85% of children showed impaired lung function after mild COVID-19.
- Lung clearance index (LCI) was most affected, with many patients still showing abnormalities 5 months post-infection.
- Children had fewer severe pulmonary issues and symptoms compared to adults.

## Abstract

Although the majority of patients suffering from COVID-19 (coronavirus disease 2019) did not require hospitalization, data on the persistence of pulmonary sequelae after a mild SARS-CoV-2 (severe acute respiratory disease coronavirus 2) infection in patients without pre-existing respiratory diseases are virtually missing.

Pulmonary function (spirometry, diffusion capacity for carbon monoxide (DLCO), and lung clearance index (LCI)) was assessed 4–12 weeks after SARS-CoV-2 infection in non-hospitalized patients aged 6–60 years. Acute and persisting COVID-19-related respiratory symptoms were ascertained, and the presence of other acute respiratory infection pathogens was checked via a multiplex-PCR approach from pharyngeal swabs. Participants with impaired lung function underwent a follow-up examination 3 months later. To complement the initial analysis, a retrospective z-score analysis of lung function parameters was conducted.

110 patients (90 adults, 20 children) were included. In 45 adults (50%) and 17 children (85%), at least one pulmonary function test indicated an impaired lung function, particularly the LCI. Despite overall improvement between baseline and follow-up, 9 of 13 (69.2%) children and 35 of 42 (83.3%) adults with initial impairment still showed abnormal values about 5 months post SARS-CoV-2 infection.

Specific respiratory symptoms were linked to lower spirometry and DLCO values. In 25 patients (40.3%) with abnormal lung function, and in 20 participants (43.5%) with normal pulmonary function, pathogens were detected at t1. The retrospective z-score analysis closely mirrored the initial findings.

Critical pulmonary impairment after mild COVID-19 is rarely detected by spirometry and DLCO but may affect the LCI. Within 3 months, impaired pulmonary function improved in most patients. Children were less affected by severe pulmonary sequelae and respiratory complaints than adults. Complaints like dyspnoea or chest pain may be an early indicator of lung function impairment, suggesting that further diagnostic tests for treatable post-COVID-19 complications may be needed. Additionally, PCR-based screening for additional respiratory pathogens may help avoid misinterpretation of lung function results post SARS-CoV-2 infection.

Retrospectively registered in ClinicalTrials.gov (ID NCT06318208) and German Clinical Trials Register (ID DRKS00030025).

The online version contains supplementary material available at 10.1186/s12890-025-04007-y.