It’s easy to assume that only people who were very sick with COVID-19 go on to have lasting symptoms. A large international study published in JAMA suggests otherwise: about 90% of people who developed long COVID had started out with a mild infection that didn’t require a hospital stay.

What is long COVID?

Long COVID refers to symptoms that continue or develop weeks to months after a COVID-19 infection. Symptoms vary widely, but common ones include ongoing fatigue, body aches, mood changes, trouble thinking clearly (often called “brain fog”) and breathing problems. For some people, these symptoms make it hard to work, exercise or keep up with daily life.

How the study was done

Researchers working with the Global Burden of Disease long COVID collaborators pooled data from 54 studies and two large medical record databases. Altogether, the analysis covered more than 1.2 million people in 22 countries who had symptomatic COVID-19 infections in 2020 and 2021.

The team focused on three groups of symptoms that are among the most commonly reported in long COVID:

• Ongoing fatigue with body pain or mood swings
• Cognitive problems, such as forgetfulness or difficulty concentrating
• Ongoing respiratory problems, such as shortness of breath or cough

They then estimated how many people still had at least one of these symptom groups three months after their infection.

What the researchers found

• About 6% of people with a symptomatic infection had at least one of the three long COVID symptom groups at three months.
• Roughly 90% of long COVID cases came from people whose initial illness was mild.
• Hospitalized patients had a higher individual risk of long COVID than people who weren’t hospitalized. But because the vast majority of infections were mild, mild cases still made up most long COVID cases overall.
• Women were more likely than men to develop long COVID, according to the analysis.

In a summary written for The Conversation, the researchers stressed that long COVID can seriously affect people’s health and ability to work, and that finding effective, affordable treatments should be a priority.

New tools to study long COVID

Because long COVID looks so different from person to person, researchers are working on ways to sort patients into groups. One example is a machine learning tool designed to scan electronic health records and identify common symptom patterns, so patients can be classified into subtypes. The hope is that this kind of approach could eventually help doctors match treatments to the type of long COVID a person has.

What this means for you

A mild case of COVID-19 isn’t a guarantee that you’ll recover without lingering effects. A few practical steps can help:

• Reduce your risk of infection. Staying up to date on recommended COVID-19 vaccines lowers the chance of getting sick, and studies suggest vaccination may also lower the risk of long COVID.
• Give yourself time to recover. After any infection, ease back into exercise and demanding work rather than pushing through exhaustion.
• Track your symptoms. If fatigue, brain fog, breathlessness or other symptoms last more than a few weeks, write down what you notice and when.
• Talk to your doctor. Long COVID is a recognized condition. Your provider can rule out other causes and may refer you to a specialist or a post-COVID clinic.

The bottom line

Most people with long COVID started out with a mild infection. While being hospitalized raises a person’s risk, mild cases are so common that they account for the large majority of long COVID. If symptoms linger after you’ve been sick, they’re worth taking seriously and discussing with a healthcare provider.

This article is for general information and isn’t medical advice. Talk with your healthcare provider about your individual needs.

Sources

• Global Burden of Disease Long COVID Collaborators. Estimated global proportions of individuals with persistent fatigue, cognitive, and respiratory symptom clusters following symptomatic COVID-19. JAMA, 2022.
• The Conversation: Long COVID stemmed from mild cases of COVID-19 in most people
• News-Medical: New machine learning tool can shed light on chronic COVID symptoms