A recent study posted to the medRxiv* preprint server described coronavirus disease 2019 (COVID-19) sequelae developed in non-hospitalized young adults more than six months after COVID-19 infection. Although extensive research has been conducted on the manifestation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) symptoms in infected patients, data about the persistence of symptoms and their effects on the patients post-infection are insufficient.
About the study
The present LoCoMo (Long COVID in Military Organisations) study aimed to evaluate the long-term sequelae of COVID-19 infections, particularly the adverse impact on the pulmonary, neurological, cardiovascular, ophthalmological, male reproductive, renal, psychological, and general health of the patient based on laboratory and serological parameters.
The study involved Swiss army recruits of ages between 18 to 30 years who were tested for the presence of SARS-CoV-2 in their saliva samples using SARS-CoV-2 rapid antigen tests. The participants then filled out a consent form and provided baseline demographic data, including sex, age, body weight, body height, COVID-19 test result, vaccination status, smoker status, comorbidities, and education level.
The study was evaluated based on a non-invasive test battery that assessed general symptoms like fatigue using the Chalder fatigue scale (CFQ-11) and mood states 2 (POMS2) profile. At the same time, kidney function was measured using cystatin C and creatinine levels along with the glomerular filtration rate (eGFR). White cell counts and C-reactive protein (CRP) were also evaluated. Pulmonary function was assessed to estimate interstitial damage or damage to microcirculation and total lung capacity (TLC).
Cardiovascular sequelae were measured based on the presence of the marker for congestive heart failure, N-terminal pro-Brain natriuretic peptide (NT-proBNP). A cardio-pulmonary exercise test (CPET) evaluated the cardiovascular function while the olfactory function was evaluated by threshold-discrimination-identification (TDI) score, which indicated normosmia with a TDI of 31 and more, hyposmia with TDI less than 31, and functional anosmia with TDI less than or equal to 16.
Ophthalmic examination included tests like color fundus photography (CF), optical coherence tomography angiography (OCTA) scanning, autofluorescence imaging, and ultra-widefield (UWF) CF. Sperm count, the status of mental health, and neutralizing antibody (nAb) titers of individuals of different vaccination statuses were also evaluated.
The study results showed that among the 501 participants involved in the study, 5.6% were female candidates, and the median age of the population was 21 years. Six months after COVID-19 infection, participants had a higher body mass index (BMI), higher blood cholesterol, higher low-density lipoprotein (LDL) levels, and lower aerobic thresholds compared to the control group, which had no history of COVID-19 infections, and a higher fatigue level compared to the asymptomatic COVID-19 patients.
Significant hyposomia was observed in a higher number of COVID-19 cases patients less than six months after infection than in older cases. Compared to the control cases, a poorer sperm count was observed in recent infection cases than in less recent cases. Anxiety levels and scores of COVID-19-related post-traumatic stress disorder (PTSD) were notably higher in COVID-19 cases less than six months post-infection as compared to less recent infection cases.
A limited ability to neutralize SARS-CoV-2 antibodies was observed in COVID-19-recovered patients who were unvaccinated while recovered and fully vaccinated individuals had a higher neutralization capacity.
The study findings showed that non-hospitalized COVID-19-infected young adults mostly recovered from mild SARS-CoV-2 infection and experienced a lower overall impact of the infection on the human body than older, hospitalized patients with comorbidities. However, even mild infections have been noted to cause significant sequelae that persist over several months after the infection. Effects like hyposomia, fatigue, reduced psychological scores, and an adverse impact on the male reproductive system were also found.
The researchers believe that the LoCoMo study can be further used to analyze COVID-19 sequalae in other populations, especially young females. Understanding the long-term impact and persistence of COVID-19 sequelae can facilitate the improvement of COVID-19 policies with better knowledge of sequalae pathophysiology.
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.