The incidence of post-COVID conditions among patients who had received a previous COVID-19 diagnosis

By Tarun Sai LomteReviewed by Danielle Ellis, B.Sc.May 26 2022

In a recent study published in the Morbidity and Mortality Weekly Report (MMWR), researchers evaluated the incidence of post-coronavirus disease (post-COVID-19) conditions among adults in the United States (US).

Many people with a history of infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have reported long-term symptoms four weeks or more after acute infection. This condition is termed long COVID or post-COVID-19 syndrome.

About the study

In the current study, researchers assessed the incidence of 26 conditions attributable to long COVID among the US adult population previously diagnosed with COVID-19 (cases). Electronic health records (EHRs) of individuals aged 18 years or above were accessed for the March 2020-to-November 2021 period. The authors implemented a retrospective matched cohort design to examine EHRs. The incident conditions were compared to matched individuals (controls) who had no evidence of COVID-19 in EHRs.

There were 353,164 case patients with a confirmed COVID-19 diagnosis in the past or a positive SARS-CoV-2 test result (index encounter) in an inpatient, emergency department (ED), or outpatient setting. More than 1.6 million controls had a visit in that month (index encounter for controls) who did not have a positive SARS-CoV-2 test or did not receive a COVID-19 diagnosis. They matched controls with cases in a 5:1 ratio and age-stratified subjects into two groups: 18 – 64 years and ≥ 65 years.

Subjects were excluded if they had a history of any assessed condition in the year preceding the index encounter. Individuals were followed up for 30-to-365 days post index encounter till the first occurrence of an incident condition. The authors calculated incidence rates per 100 person-months and risk ratios (RRs) with 95% confidence intervals (CIs)

Findings

Overall, more than 38% of cases and 16% of controls experienced an incident condition. In the 18 – 64 years group, 35.4% of cases had an incident condition compared to 14.6% of controls, and 45.4% of cases and 18.5% of controls in the older age experienced an incident condition. The absolute risk difference between the proportion of cases and controls developing an incident condition was 20.8 and 26.8 percent points for those in the 18 – 64 years and ≥ 65 years age groups, respectively.

This meant that one in four (≥ 65 years) and five (18 – 64 years) COVID-19 survivors experienced an incident condition that could be attributed to prior SARS-CoV-2 infection. Multiple systems were affected and included pulmonary, cardiovascular, renal, hematologic, endocrine, musculoskeletal, gastrointestinal, psychiatric, and neurologic signs/symptoms.

The highest RR was observed for acute pulmonary embolism for the ≥ 65 years (RR: 2.2) and 18 – 64 years (RR: 2.1) age groups, followed by respiratory symptoms with an RR of 2.1 for either group. In the ≥ 65 years age group, RRs were higher for cases than controls for all incident conditions ranging from substance-related disorder (RR: 1.2) to acute pulmonary embolism.

In the 18 – 64 years group, RRs for cases were higher than control patients for 22 incident conditions that ranged from anxiety (1.1) to acute pulmonary embolism. Differences in cerebrovascular disease (CVD), mood disorders, substance-related disorders, and other mental conditions were not significant in this age group.

The authors observed a significantly higher risk for cardiac dysrhythmia in 18 – 64 years (RR: 1.7) than patients aged 65 years or above (RR: 1.5). Notably, cases in the 18 – 64 years group had higher risks for ten incident conditions than patients in the older age group, and the conditions were muscle disorders, thromboembolic events, CVD, renal failure, diabetes type 2, neurologic conditions, anxiety, mood disorders, substance-related disorders, and other mental conditions.

Conclusions

The study revealed that COVID-19 survivors were at greater odds of experiencing incident conditions attributable to their prior COVID-19 diagnosis than controls. The highest risks were observed for acute pulmonary embolism and respiratory symptoms.

COVID-19 survivors aged 65 years or higher were at an elevated risk for neurologic and four mental health conditions (anxiety, substance-related disorder, mood disorder, and other mental conditions). These findings do not represent all US adults or cases infected with the more recent SARS-CoV-2 variants. Moreover, the study did not account for COVID-19 vaccination and potential confounders.

With an increase in the proportion of COVID-19 survivors, the proportion of those experiencing long COVID would also increase. Thus, it is critical to perpetuate COVID-19 preventive policies and routinely monitor COVID-19 survivors for post-COVID-19 conditions so as to lower the incidence and impact of long COVID-19, especially in the elderly.