Sarah Wulf Hanson is Senior Research Scientist in Global Health Metrics at the University of Washington and Theo Vos is Professor of Health Metrics at the University of Washington.
The big idea
Even mildCases can have serious and long-lasting impacts on people’s health. That’s one of the key findings of our most recent cross-country study of long COVID-19 — or long COVID — recently published in the Journal of the American Medical Association.
is defined as the continuation or development of symptoms three months after initial infection with SARS-CoV-2, the virus that causes COVID-19. These symptoms persist for at least two months after onset without any other explanation.
We found that a staggering 90% of people living with long-term COVID-19 had only mild illness with COVID-19 to begin with. However, after developing a long COVID, the typical person experienced symptoms such as fatigue, shortness of breath, and cognitive issues such as brain fog — or a combination thereof — that interfered with day-to-day functioning. These symptoms had health implications that were just as serious as the long-term effects of traumatic brain injury. Our study also found that women are twice as likely as men and four times as likely as children to have long-term illness from COVID.
We analyzed data from 54 studies that reported over 1 million people from 22 countries who had symptoms of COVID-19. We counted how many people with COVID-19 developed clusters of new long COVID symptoms and determined how their risk of getting the disease varies by age, gender and whether they were hospitalized for COVID-19 .
We found that patients hospitalized for COVID-19 were at greater risk of developing long-term COVID-19 infection — and having longer-lasting symptoms — compared to people who were not hospitalized were. However, since the vast majority of COVID-19 cases do not require hospitalization, many more cases of long-lasting COVID have emerged from these milder cases, despite their lower risk. Among all people with long COVID, our study found that nearly one in seven still had these symptoms a year later, and researchers still don’t know how many of these cases could become chronic.
Why it matters
Relatively little is known about long COVID compared to COVID-19.
Our systematic, cross-country analysis of this state produced findings that shed light on the potentially high human and economic costs of a protracted COVID around the world. Many people living with this condition are working-age adults. Being unable to work for many months could result in people losing their income, livelihood and home. For parents or caregivers living with long COVID, the condition can leave them unable to care for loved ones.
Based on the spread and severity of long COVID, we think it is keeping people from work and therefore contributing to the labor shortage. Long COVID could also be a factor in how people losing their jobs disproportionately affect women.
We believe finding effective and affordable treatments for people living with long COVID should be a priority for researchers and research funders. Long COVID clinics have opened to provide specialized care, but the treatments they offer are limited, inconsistent and can be costly.
Long COVID is a complex and dynamic condition – some symptoms disappear, then return and new symptoms emerge. But researchers don’t yet know why.
While our study focused on the three most common symptoms associated with long COVID that affect day-to-day functioning, the condition can also include symptoms such as loss of smell and taste, insomnia, gastrointestinal issues, and headaches, among others. But in most cases, these additional symptoms appear along with the main symptoms for which we have made estimates.
There are many unanswered questions about what predisposes people to a long COVID. For example, how do different risk factors, including smoking and a high body mass index, affect the likelihood of people developing this disease? Does reinfection with SARS-CoV-2 change the risk of a long COVID? Also, it is unclear how protection from long-dated COVID changes over time after a person has been vaccinated or boosted against COVID-19.
COVID-19 variants also offer new puzzles. Researchers know that the Omicron variant is less lethal than previous strains. Early evidence shows a lower risk of long COVID from Omicron compared to previous strains, but far more data is needed.
Most of the people we studied were infected with the deadlier variants that were in circulation before Omicron became dominant. We will continue to expand our research on Long COVID as part of the Global Burden of Disease study – which estimates deaths and disabilities from all diseases and injuries in every country in the world – to get a clearer picture of how the long-term toll is unfolding changed by COVID-19 after the arrival of omicron.
This article is republished by The conversation under a Creative Commons license.