A Detailed Study of Patients with Long-Haul COVID

The following is an extract from a major study on long-haul COVID published in June 2021, done by Fair Health, an independent nonprofit that collects data for and manages the largest database of privately billed health insurance claims in the United States. Please go to the original study for references and citations.

Many patients recover from COVID-19 within a few weeks, but some exhibit persistent or new symptoms more than four weeks after first being diagnosed. These post-COVID conditions can last for months—even nine months, according to one study—and may be experienced by 10 to 30 percent of COVID-19 patients. The conditions can include, among others, fatigue, cognitive difficulties (sometimes called “brain fog”), headache, numbness /tingling, loss of smell or taste, dizziness, heart palpitations, chest pain, shortness of breath, cough, sore throat, joint or muscle pain, excessive sweating, insomnia, depression, anxiety and fever. Patients with COVID-19, after the first 30 days of illness, are at higher risk of death than people who have not had COVID-19. 

Because this phenomenon is so new, much remains unknown about it. Even the name is unsettled: Patients with post-COVID conditions are variously referred to as having long-haul COVID, long COVID, post-COVID syndrome or post-acute sequelae of COVID-19. The causes of long-haul COVID are still unknown. Theories include persistent immune activation after the acute phase; initial damage from the virus, such as damage to nerve pathways, that is slow to heal; and persistent presence of low-level virus.

Many studies of long-haul COVID have been relatively small. The study thought to be the largest to date, which made use of US Department of Veterans Affairs national healthcare databases, involved 73,435 non-hospitalized patients with COVID-19 and 13,654 hospitalized patients with COVID-19, as well as approximately 5 million controls. Although the present study is a descriptive analysis without a control group, it includes more patients with COVID-19—a total of 1,959,982. To FAIR Health’s knowledge, this is the largest population of COVID-19 patients so far studied for post-COVID conditions. 

To perform this analysis, FAIR Health drew on longitudinal data from its database of over 34 billion private healthcare claim records from 2002 to the present. The nation’s largest such repository, it is growing by over 2 billion claim records per year. All patients in the longitudinal dataset who had been diagnosed with COVID-19 from February to December 2020 were included, except for those with certain preexisting conditions (such as cancer and chronic kidney disease) that might have acted as confounders. The remaining 1,959,982 patients were studied for their case characteristics, such as age, gender and reaction to COVID-19 (i.e., asymptomatic, symptomatic, hospitalization, loss of taste or smell only). They were further studied for the prevalence of post-COVID conditions 30 days or more after their initial diagnosis with COVID-19. Their post-COVID conditions were analyzed, with the most common conditions identified. Particular attention was given to age and gender, mental health conditions and death.

Among the key findings: 

• Of patients who had COVID-19, 23.2 percent had at least one post-COVID condition. 

• Post-COVID conditions were found to a greater extent in patients who had more severe cases of COVID-19, but also in a substantial share of patients whose cases lacked symptoms. Of patients who were hospitalized with COVID-19, the percentage that had a post-COVID condition was 50 percent; of patients who were symptomatic but not hospitalized, 27.5 percent; and of patients who were asymptomatic, 19 percent. 

• The five most common post-COVID conditions across all ages, in order from most to least common, were pain, breathing difficulties, hyperlipidemia, malaise and fatigue, and hypertension. 

• The ranking of the most common post-COVID conditions varied by age group. For example, in the pediatric population (0-18), pain and breathing difficulties were the top two conditions, as in the all-ages cohort, but intestinal issues, rather than hyperlipidemia, were the third most common. 

• Most of the post-COVID conditions that were evaluated were associated more with females than males. In the case of 12 conditions, however, males more commonly had the condition diagnosed than females. For example, of patients who had post-COVID cardiac inflammation, 52 percent were male and 48 percent female. By age, the largest share (25.4 percent) with this condition was found in a young cohort—individuals aged 19-29. 

• Of the four mental health conditions evaluated as post-COVID conditions, anxiety was associated with the highest percentage of patients after COVID-19 in all age groups. Depression was second, adjustment disorders third and tic disorders fourth. 

• The odds of death 30 days or more after initial diagnosis with COVID-19 were 46 times higher for patients who were hospitalized with COVID-19 and discharged than patients who had not been hospitalized. Of COVID-19 patients who were hospitalized and discharged, 0.5 percent died 30 days or more after their initial diagnosis. 

• Among COVID-19 patients with preexisting conditions, intellectual disabilities were associated with the highest odds of death 30 days or more after initial COVID-19 diagnosis.