Two new studies offer fresh insights into long COVID, with the first noting a greater neurological, cognitive, and fatigue impact compared with long-term symptoms after similar respiratory diseases, and the second demonstrating that a fourth of young Marines who contracted COVID-19 went on to develop long COVID.
Seven symptoms more common with long COVID
In the first study, published today in JAMA Network Open, researchers used data from the UK Biobank to compared postacute infection syndromes (PAIS) among patients with COVID-19 to other lower respiratory tract infections (LRTIs). They showed that long-COVID patients have an increased risk of seven specific symptoms.
A total of 191,710 eligible participants identified since March 1, 2020, were included in the study. Of those, 1,153 were hospitalized with COVID-19, 1,304 were hospitalized with other LRTIs, and 189,253 uninfected patients were used as a reference group.
Patients hospitalized with COVID-19 were much more likely to report PAIS symptoms including loss of taste (odds ratio [OR], 2.27; 95% confidence interval [CI], 1.87 to 2.75) and severe fatigue (OR, 2.18; 95% CI, 1.70 to 2.81) compared to the reference group. Overall, COVID patents were more likely to report 23 of 45 symptoms compared to the controls.
Compared to patients hospitalized for other LRTIs, COVID patients were more at risk for seven particular symptoms, including loss of smell (OR, 1.80; 95% CI, 1.34 to 2.42), loss of taste (OR, 1.52; 95% CI, 1.13 to 2.03), rapid heart rate upon standing (OR, 1.60; 95% CI, 1.12 to 2.29), problems with thinking (OR, 1.36; 95% CI, 1.14 to 1.62), bone pain (OR, 1.33; 95% CI, 1.06 to 1.67), mild fatigue (OR, 1.19; 95% CI, 1.01 to 1.40), and severe fatigue (OR, 1.49; 95% CI, 1.02 to 2.17).
Patients with LRTIs were more likely to report a lingering persistent cough than were COVID patients.
"Compared with other LRTIs, COVID-19 appeared to impose an extra burden of neurological, cognitive, and fatigue symptoms,” the authors concluded.
25% of Marines developed long COVID
The second study, published in The Lancet Regional Health Americas, describes how 25% of previously healthy US Marines showed signs of long COVID following even mild or asymptomatic COVID-19.
In the study, 899 Marines (91.7% male) who tested positive for COVID-19 by polymerase chain reaction testing were followed up for almost a year to determine risk factors for developing long COVID, which the authors defined as persistent symptoms at least 4 weeks after symptom onset or diagnosis. The authors found a 24.7% prevalence of long COVID.
The Marines were young (median age, 18) and healthy, having passed a number of Marine physical fitness tests prior to study enrollment. The participants were asked to complete a survey about COVID infection and symptoms. Overall, 197 Marines (24.7%) developed persistent symptoms after COVID infection.
The most prevalent symptoms reported by Marines were loss of taste and/or smell (41.6%), shortness of breath (37.6%), and cough (22.8%). When compared with a pre-COVID cohort of Marines, the authors found the Marines reporting persistent COVID symptoms had slower running times on fitness tests.
The authors said their findings are important in considering the implications of long COVID on a young and previously healthy workforce. Long COVID could "decrease work productivity and increase healthcare costs," they wrote.
A total of 307 participants (34.1%) had an asymptomatic infection. Among the 195 who described the severity of their infection, 77.4% reported a predominately mild illness, 20.0% reported moderate disease, and 2.6% reported severe illness.
Even in young healthy populations with very mild acute illness a proportion of infected individuals develop long-lasting symptoms
"The risk of long-term sequelae secondary to acute SARS-CoV-2 infection varies across studies; however, even in young healthy populations with very mild acute illness a proportion of infected individuals develop long-lasting symptoms," the authors wrote.
