A quarter of long Covid disease patients suffered from impaired pulmonary function up to a year after recovering from the initial infection.
This is the findings of a recent (not peer reviewed) study posted to the Preprints with The Lancet SSRN server, in which researchers evaluated the impairment of pulmonary function in people suffering from post-acute sequelae of Covid-19 (PASC) or long coronavirus disease (long Covid) symptoms after acute respiratory infections.
Respiratory infections like Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS) have been associated with reduced pulmonary function for months after recovering from the infection. While Covid-19 vaccines have successfully limited the severity and spread of SARS-CoV-2 infections, a number of severe Covid patients continue to experience symptoms long afterwards.
Fatigue, myalgia and dyspnea are commonly reported symptoms, and recent studies show that lower diffusing capacity for carbon monoxide (DLCO) and an associated reduction in the alveolar volume is the prevalent lung abnormality in PASC patients.
These findings are primarily based on hospitalised patients: persistent impairments with pulmonary functions have been linked to prolonged hospitalisation, ventilator use, and ICU admissions.
While studies have reported improvement in pulmonary function with time, the impact of Covid-related pulmonary function impairments on the overall quality of life and associations with other Covid symptoms remains unclear.
About the study
In the present study, led by a team from Amsterdam University Medical Centre, University of Amsterdam, the researchers conducted a longitudinal analysis of a prospective cohort to understand pulmonary function kinetics in hospitalised and non-hospitalised Covid patients. They also evaluated pulmonary function impairment and its relationship to other PASC symptoms and health-related quality of life (HRQL) for varying severities of SARS-CoV-2 infections.
The RECoVERED cohort in this study comprised non-hospitalised and hospitalised people aged between 16 and 85 with SARS-CoV-2 infections confirmed from positive polymerase chain reaction (PCR) tests.
In addition, participants for whom at least one follow-up measurement of pulmonary function was available, were included.
Information on the occurrence and duration of PASC symptoms was collected using a questionnaire, and medical history and socio-demographic data were obtained from interviews and medical records. During the acute phase of SARS-CoV-2 infections, physical measurements such as respiratory rate, oxygen saturation, and heart rate were collected during enrolment, as well as one week and one month after enrolment.
Pulmonary function was measured based on DLCO at multiple time points after the onset of Covid. Other measured parameters included forced vital capacity, pulmonary diffusion capacity, vital capacity, forced expiratory volume in one second, and alveolar volume. The DLCO measurements were corrected based on haemoglobin measurements.
A self-administered health survey questionnaire was used to assess HRQL at one and 12 months of follow-up. This questionnaire assessed well-being, functional status, and overall health.
Results
The findings reported that at 12 months of follow-up, a quarter of the participants continued to have impaired pulmonary function, with mild, moderate, and severe SARS-CoV-2 infections accounting for 11%, 22%, and 48% of these cases, respectively. While the DLCO values improved over time, three or more comorbidities and severe or critical initial SARS-CoV-2 infections were associated with decreased pulmonary function improvement rates. However, the HRQL values showed progressive improvement irrespective of pulmonary function impairment.
Parameters such as vital and forced vital capacity also showed improvements over time in patients with severe or moderate initial SARS-CoV-2 infections, indicating that Covid-19-associated lung damage could be reversed. Diffusion capacity abnormality was the predominantly observed pulmonary function impairment for up to a year, and there were significant differences in diffusion capacity across Covid-19 severities.
While previous studies have reported physical and pulmonary function impairments and reduction in the quality of life associated with muscle weakness after acute lung injuries, the authors said these findings were in contrast to those that reported persistent symptoms and reductions in HRQL a year after recovering from Covid-19.
One of the limitations of this study was the inability to assess the pulmonary function impairments specifically associated with SARS-CoV-2 infections due to the unavailability of pulmonary function testing results before the onset of Covid.
Overall, the results suggested that 25% of Covid patients experienced impaired pulmonary function up to a year after recovering from the initial infection. However, this did not seem to impact the health-related quality of life significantly.
Furthermore, the single-breath diffusion capacity parament differed significantly according to the severity of the initial SARS-CoV-2 infection, potentially explaining the slower recovery rate of patients with severe Covid.
Study details
One-Fourth of COVID-19 Patients Have an Impaired Pulmonary Function after 12 Months of Illness Onset
Hugo van Willigen, Elke Wynberg et al.
Posted on The Lancet pre-print server on 24 February 2023
Abstract
Background
This longitudinal study evaluates the extent of impaired pulmonary function over time after SARS-CoV-2 infection across the full spectrum of COVID-19 severity.
Methods
Pulmonary function was measured by diffusing capacity for carbon monoxide (DLCO) at one, six, and twelve months after illness onset. Additionally, data on sociodemographics, clinical characteristics, symptoms, and health-related quality of life (HRQL) were collected. Pulmonary function and determinants were modelled over time using mixed-effect linear regression. Determinants of pulmonary impairment at 12 months since illness onset were identified using logistic regression.
Findings
Between May 2020 and December 2021, 301 of 349 participants underwent at least one pulmonary function test. After one year of follow-up, 25% of the participants had an impaired pulmonary function which translates in 11%, 22%, and 48% of the participants with mild, moderate and severe/critical COVID-19. Improvement in DLCO among the participants continued over the period across one, six and twelve months. Having more than three comorbidities (p<0·001) and initial severe/critical illness (p<0·001) were associated with slower improvement of pulmonary function over time, adjusted for age and sex. HRQL improved over time and was not different to those without impaired pulmonary function.
Interpretation
The prevalence of impaired pulmonary function after twelve months of follow-up, was still significant among those with initially moderate or severe/critical COVID-19. However, those who continued to have impaired pulmonary function after one year did not have impaired HRQL.
See more from MedicalBrief archives:
Long COVID impacts heart, lung and kidney – Scottish study
Are severe Covid- pneumonia patients on ventilation longer than needed? US study
Long COVID breathlessness: Novel scans uncover hidden lung damage
Concerns about lasting heart damage in COVID-19 patients — 2 German studies