The Long COVID's Long Shadow: CDC Researchers Document Health Conditions After Acute Phase Is Over

One in 4 COVID-19 patients in the 18-64 age group experienced at least one of the 26 conditions that may be associated with COVID-19, according to CDC researchers. However, the study did not differentiate the risk by vaccination status or SARS-CoV-2 strain, both of which may affect the risk of post-acute conditions and symptoms.

Even if the risk of hospitalization and death from COVID-19 seems to be easing up as the result of vaccination and the circulation of less virulent strains of SARS-CoV-2, the diseases pose the risk of causing health conditions and persistent symptoms well after the acute infection is over.

The risk of “long COVID,” as it has come to be called, is informing public health policy and also shaping public attitudes toward COVID-19.

A CDC study of long COVID published in the agency’s Morbidity and Mortality Weekly Reportlast week added to the understanding of long COVID — and probably to the dread of it.

The overall and simplest finding was that 1 in 5 people in the 18-64 age group and 1 in 4 among those age 65 and older who were diagnosed with COVID-19 or had a positive test for the SARS-CoV-2 had a condition afterward that might be traced back to COVID-19.

One of the takeaways from the researchers was the need for routine assessment for post-COVID conditions.

“These findingscan increase awareness for post-COVID conditions and improve post-acute care and management of patients after illness,” wrote lead author Lara Bull-Otterson, Ph.D., a senior epidemiologist at the CDC, and her colleagues.

But Bull-Otterson and her fellow researchers, all of whom are members of the CDC COVID-19 Emergency Response Team, also noted some limitations to their study that leaves open the possibility that long COVID is less of a risk now than it was during the early months of the pandemic.

For one thing, as they mention, their study did not filter by vaccination status. Long COVID may be less of a risk for those who are vaccinated (and boosted) than those who are not. In addition, the study was based on data from electronic health records (EHR) from March 2020 through November 2021, the period before the omicron variant became the dominant SARS-CoV-2 strain. Different strains of SARS-CoV-2 may pose different long COVID risks.

Still, this study is one of the largest studies of long COVID so far and therefore one of the most informative. Bull-Otterson and her colleagues used the Cerner Real-Word Data database to conduct their study. Cerner is one of largest EHR companies in the country and its database includes more 63 million unique adult records. The data used by the CDC researchers was “deidentified” and had names and other information removed. They sifted through the Cerner database to identify about 353,000 adult cases —people 18 and older diagnosed with COVID-19 or with a positive test for the virus. The EHR data they looked was from March 2020 through November 2021 Those cases were compared with 1.64 million controls. They identified 26 conditions that other research has attributed to post-COVID illness that range from heart failure to sleep disorders to smell and taste “disturbances” and then used the EHRs to compare the frequency of their occurrence among the cases with the frequency among the controls.

Overall, they found that 38.2% of the cases experienced one of the 26 conditions compared with 16% of the controls. The case versus control difference was largest for acute pulmonary embolism: Cases were more than twice as likely to have an acute pulmonary embolism than the controls.

Among the patients 65 and older, the risk was higher for the cases for all 26 conditions the researchers looked a. Among those 18-64, the risk was higher for 22 conditions. There was no difference between the cases and controls when it came to cerebrovascular disease, mood disorders, substance abuse-related disorders and a catch-all category of other mental health conditions.

Bull-Otterson and her colleagues discuss a couple of methodological reasons that their study might have overestimated the risk of long Covid. For one, physicians and other clinicians may have been more likely to document one the 26 conditions among the COVID-19 patients because research had identified post-Covid conditions, so they were on the lookout for them in their patients who experienced a COVID-19 infections.

It is also possible, they said, that case patients were more likely not to have an existing condition documented in their EHR prior their COVID-19 diagnosis.

On the other hand, they said that the control group, which consisted of people seeking healthcare, were sicker than a normal population and therefore this case-control comparison underestimated the post-COVID risk among the cases.