Two new studies offer details about long COVID, with post-acute symptoms linked to disease severity in a Swedish cohort, and a Dutch study showing that almost half of COVID-19 patients reported lingering symptoms 90 days after infection.
The first study, an analysis in the Journal of Internal Medicine, identifies several characteristics associated with a higher likelihood of developing long COVID, with the condition most common in patients who required treatment in the intensive care unit (ICU).
The study included 204,805 Swedish adults with confirmed COVID-19 infections between Mar 1, 2020, and Jul 31, 2021. All participants lived in Stockholm County. Study subjects were followed for the outcome from 90 to 360 days after their first positive SARS-CoV-2 test.
Of the participants, post-COVID condition (PCC) was diagnosed in 1% among individuals not hospitalized for their COVID-19 infection, 6% among the hospitalized, and 32% among ICU-treated patients.
Women, middle-aged more at risk
Females were more likely to receive a PCC diagnosis, as were middle-aged adults. Elderly adults were not at increased risk for PCC, the authors said. Disease severity, however, was the most predictive factor of PCC.
"Among hospitalized and ICU-treated individuals, the occurrence of PCC diagnosis was associated with an increased length of stay in the hospital/ICU during the acute infection," the authors wrote. "Among nonhospitalized individuals, 83% had their PCC diagnosed in primary care only, compared to 72% and 31% for the hospitalized and ICU-treated individuals, respectively."
The most common symptoms seen upon PCC diagnoses for non-hospitalized patients were fatigue (seen in 29%) and anxiety (21%). Difficulty breathing was seen in both hospitalized (25%) and ICU-treated (41%) individuals.
The authors said, however, that many participants had documented health visits related to anxiety and fatigue before COVID-19 infection.
"Our finding of around 50%–60% of individuals with a PCC diagnosis having symptom diagnoses concordant with the WHO definition of PCC before the acute SARS-CoV-2 infection indicates that some of the disease burden could be wrongly attributed to COVID-19 or that COVID-19 accentuates pre-existing conditions," they concluded.
In a news release from Wiley, the journal's publisher, first author Pontus Hedberg, MD, said, "Our understanding of health effects beyond the acute SARS-CoV-2 infection is continuously improving. In this study, we observed a marked difference in the occurrence of post COVID-19 condition diagnosis across different severities of the acute infection.
"Furthermore, the elevated outpatient primary and specialist care use indicates poor recovery for individuals suffering from post COVID-19 condition, highlighting the urgent need to better understand this condition and its potential resolution over time."
Vaccine protective against loss of smell, taste only
The second study is based on a Dutch cohort during the Delta wave. It shows that, 3 months after acute infection, 48.5% of COVID-19 patients reported at least one significantly elevated symptom, compared with 29.8% of test-negative controls and 26.0% of population controls.
Moreover, vaccination was significantly protective for loss of smell and taste but not for other symptoms 3 months after acute infection.
The study was published in the Journal of Infectious Diseases. In total, 9,166 cases, 1,698 symptomatic but test-negative controls, and 3,708 population controls were enrolled. Case-patients had a positive polymerase chain reaction (PCR) test from May 19 to Dec 13, 2021.
Of the 41 symptoms assessed, only 13 were increased in COVID-19 patients compared to controls. Fatigue (31.1%), loss of smell (12.0%), labored breathing (16.4%), concentration difficulties (15.0%), and difficulties in busy environments (13.1%) showed the largest difference in prevalence.
In COVID-19 patients who had been previously vaccinated, vaccination was protective only against loss of taste and smell, and no other long-COVID symptoms.