We get a lot of questions as to what is the best scientific evidence that demonstrates various aspects of Long Covid. To facilitate our sharing of this information, we have put together our list of some of the top peer-reviewed scientific publications on Long Covid. We have chosen these papers because we believe that they are some of the most rigorous and well-designed studies in the field. These are not necessarily the most dramatic papers or the ones that show the biggest effect, though we believe they conclusively demonstrate the existence and severity of Long Covid. These are not our studies and we have no investment or interest in the studies, outside of looking for high-quality data on Long Covid. All scientific research is a moving target and there may be things we haven’t noticed in these papers or subsequent research that changes the interpretation. With that in mind, here are some of our top papers as of December 2023.

Long Covid prevalence

The aspect of Long Covid that we’re asked the most is how prevalent it is. This is a very difficult question to answer as each study defines Long Covid and their study population differently, leading to very different rates of Long Covid in different publications. We find that the best studies have a very clear definition of Long Covid and include a control group that allows us to see the increase in symptoms following Long Covid specifically. 

Five good studies that fit these criteria are:

1. Development of a Definition of Postacute Sequelae of SARS-CoV-2 Infection. JAMA, May 2023. This is a prospective cohort study with an uninfected control cohort that includes nearly 10,000 people from the US Recover study. The study does not focus on individual or pre-defined symptom frequency, so may provide  a better overall estimate of the risk of Long Covid. Their results show a 1.5x increased Odds Ratio for PASC and that 10% of their population is PASC positive at 6 months post infection. 
2. Postacute sequelae of COVID-19 at 2 years. Nature Medicine, August 2023. This is a cohort study that includes an uninfected control cohort with electronic health record data from 138,818 infected and 5,985,227 uninfected individuals from the US Veterans Affairs. This is a slightly different kind of analysis looking at the incidence of PASC occurring instead of the prevalence of PACS in the cohort at a specific time, but they show that over the two years post a Covid-19 infection, the incidence of PASC was 9.6%. They also show a wide range of individual sequelae with significantly increased Relative Risks. 
3. Physical and cognitive impact following SARS-CoV-2 infection in a large population-based case-control study. Nature Communications Medicine, July 2023. This is a case-control study from Iceland showing a 7% prevalence of Long Covid at 8 months.
4. Case–Control Study of Long COVID, Sapporo, Japan. Emerging Infectious Diseases, May 2023. This is a Case-control study from Japan showing increased risk of multiple Long Covid symptoms at 4-18 months in cases vs controls.
5. Risk of long COVID main symptoms after SARS-CoV-2 infection: a systematic review and meta-analysis. Scientific Reports, September 2023. This is a slightly different kind of study that reviews and compares a large number of previously-published studies reporting prevalence, incidence and risk ratios of Long Covid.