# The Clinical Research of the Chronic Cough After COVID-19 Infection

## TL;DR

This study explores the causes and characteristics of long-term cough following a SARS-CoV-2 infection, identifying risk factors and lung function changes in patients.

## Contribution

The study identifies specific clinical and pulmonary function indicators associated with chronic post-COVID-19 cough.

## Key findings

- Chronic cough patients had lower platelet counts and higher eosinophil and basophil percentages compared to acute cases.
- Pulmonary function indices like FVC, FEV1, and DLCO were significantly lower in the chronic cough group.
- Chest CT scans showed chronic group differences in lesion types and micro-nodule prevalence compared to other groups.

## Abstract

Objective: To investigate the epidemiology, clinical characteristics, and potential risk factors of chronic cough following SARS-CoV-2 infection. Methods: A total of 1434 patients with post-COVID-19 cough were categorized into acute, subacute, and chronic subgroups by cough duration, with clinical data analyzed across subgroups. Questionnaire surveys were conducted in chronic cough patients, followed by an 18–21-month follow-up. Results: 1. Significant intergroup differences were observed among the three groups in: the number of patients with rhinitis and/or pharyngitis history, cough with chest tightness, cough with pharyngeal symptoms, and sensitivity to irritating odors and cold air. 2. The chronic group had a significantly lower platelet count but higher eosinophil and basophil percentages than the acute group. 3. The chronic group showed significantly lower values than the subacute group in multiple pulmonary function indices: FVC, FEV1, FEV1/FVC, PEF, MEF25, MEF75, MEF50, MMEF75/25, MEF75%, MEF50%, MEF25%, MMEF75/25%, DLCO, and DLCO%. 4. Chest CT findings: the chronic group had significantly lower rates of infected lesions, cord-like opacities, and ground-glass shadows than the acute group, but a higher rate of micro-nodules than the subacute group. 5. At follow-up, the cough and non-cough groups differed significantly in nighttime cough scores and the proportion of cough with chest tightness, as well as in pulmonary function parameters: FVC, FEV1, PEF, PEF%, MEF75, DLCO, RV% and TLC. 6. Binary logistic regression analysis identified the nocturnal cough symptom score and cough accompanied by chest tightness as independent factors influencing persistent cough 18–21 months after SARS-CoV-2 infection. Conclusions: Patients with pre-existing upper airway inflammation, laryngeal symptoms, chemical hypersensitivity, elevated eosinophil/basophil percentages, and pulmonary micro-nodules are more likely to develop chronic post-COVID cough, presenting with partial ventilatory impairment and diffusing capacity impairments.