The study suggests that SARS-CoV-2 infection may negatively affect the health of a significant proportion of young adults.

Study: Clinical and functional assessment of SARS-CoV-2 sequelae among young marines — a panel study. Image Credit: PeopleImages.com / Yuri A / Shutterstock.com

In a recent study published in The Lancet Regional Health—Americas, researchers examined the long-term health effects of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in a cohort of United States Marines.

The long-term effects of COVID-19

Post-acute sequelase of the coronavirus disease 2019 (COVID-19) (PASC) can impact overall functioning and reduce physical fitness, thereby raising significant public health concerns, especially for individuals involved in physically demanding jobs.

Young adults who experience only mild or no symptoms of SARS-CoV-2 infection may still experience long-term effects of COVID-19, which may include but are not limited to, physical impairments, as well as mental health issues such as cognitive difficulties and depression. However, studying PASC in young adults has been challenging due to limited interactions between individuals of this age group and the healthcare system.

About the study

The present study investigated long-term complications of COVID-19 among a population of young and healthy U.S. Marine Corps recruits enrolled in the COVID-19 Health Action Response for Marines (CHARM) study during the spring and fall of 2020.

Marines who were enrolled in the original CHARM study attended follow up visits every six months after they completed the recruit training for the U.S. Marine Corps. Only study participants on active duty were included in the analysis.

All individuals enrolled in the study completed a set of detailed questionnaires that collected their medical histories, including data on SARS-CoV-2 infections, as well as both acute and persistent effects of COVID-19. Validated questionnaires and tests were also used to assess well-being, depression, anxiety, and sleep quality.

The severity of COVID-19 was self-reported on a 10-point scale and categorized as severe, moderate, or mild. The study participants also provided COVID-19 symptoms that lasted for over a month and reported any functional impairments that resulted in loss of workdays and reduced performance during fitness tests.

The fitness metrics used in the current study were based on fitness data obtained from the U.S. Marine Corps, which includes results from physical fitness tests, marksmanship assessments, and combat fitness tests. These tests, which are mandatory for all marines, are conducted during recruit training and annually thereafter. Test results of a reference cohort from 2016 to 2019 were used for comparison.

PASC was defined as persistent complications or symptoms lasting beyond four weeks after a positive COVID-19 polymerase chain reaction (PCR) test or symptom onset. Symptom reports from the study participants were assessed and categorized into 14 symptom groups.

SARS-CoV-2 infection was confirmed based on documented PCR test results, seropositivity, or self-reports. Enzyme-linked immunosorbent assay (ELISA) was used to measure serum immunoglobulin G (IgG) antibody levels, with levels above 150 used to classify individuals as seropositive.

IgG antibodies to the nucleocapsid protein were used to confirm prior SARS-CoV-2 infection. Electronic health records were also used to determine whether the participants had completed the two-dose messenger ribonucleic acid (mRNA) vaccine regimen.

Study findings

Of the 899 marines included in the study, 88.8% reported a history of SARS-CoV-2 infection, 24.7% of whom experienced persistent COVID-19 symptoms lasting at least four weeks. Among those with PASC, 10 were asymptomatic, thus indicating that even mild infections can lead to persistent health issues.

Many of the participants reported reduced productivity at work, difficulties performing their duties, and loss of workdays. Physical fitness assessments showed that marines with PASC had lower run times; however, upper body strength assessments, which included pull-ups and crunches, remained unaffected. These results suggest a lasting effect of COVID-19 on cardiopulmonary fitness.

Mental health assessments revealed that about 10% of PASC-affected individuals had high scores on the anxiety and depression scales. Cardiopulmonary symptoms such as shortness of breath, fatigue, and cough were linked to reduced aerobic performance.

Interestingly, other physical metrics of strength, such as fine motor skills tested through marksmanship tests, were not impacted. Thus,  the impact of PASC may primarily affect cardiopulmonary function rather than neuromuscular strength.

Conclusions

PASC caused significant impairments in the physical and mental health of young and healthy U.S. Marines, particularly in their aerobic performance and overall productivity. The development of cardiopulmonary symptoms of PASC, despite having a mild or almost asymptomatic SARS-CoV-2 infection, emphasizes the need for increased research on the long-term effects of PASC.