Long COVID May Have Been Overreported, Major Stanford Study Finds

A large-scale study from Stanford University in the United States has found that Long COVID may have affected fewer people for a shorter period than widely believed, raising important questions about how the condition has been tracked, diagnosed and reported since the pandemic began.

The research, which drew on 4.4 billion health insurance records from more than 244 million Americans, identified a significant flaw in the methods used by earlier studies, one that may have caused the long-term health effects of COVID-19 to be substantially overestimated.

What the Research Actually Found

Previous studies typically compared people who had tested positive for COVID-19 against those who had never been diagnosed or tested at all. The Stanford team argues this approach introduced bias, because people who are more likely to seek testing also tend to have more documented health issues on record. That creates a misleading statistical link between those health problems and COVID-19 itself.

By narrowing the comparison to only those who had tested positive versus those who tested negative, the researchers believe they produced a far more reliable picture of COVID-19's lasting health effects.

Professor Jure Leskovec, one of the study's authors, said the results were striking. "Our new study design found 98 per cent fewer Long COVID-attributable outcomes between four to 12 months after infection compared with conventional approaches applied in the same dataset," he said. He was careful to clarify the finding, adding: "This doesn't mean Long COVID is 98 per cent less common. It means that how we design these studies fundamentally changes which health effects we can reliably attribute to COVID."

Co-author Professor Steven Goodman, a professor of epidemiology and population health at the Stanford School of Medicine, suggested the condition may sit closer to other known post-viral illnesses than previously understood. "These findings indicate that Long COVID may be more similar to other extended post-viral syndromes than many have thought," he said.

The Challenge of Diagnosing Long COVID in Australia

Part of what makes this research so significant is that no clinical diagnostic test exists for Long COVID, a fact that has complicated efforts to measure its true prevalence from the outset.

The Australian government defines Long COVID as experiencing symptoms for at least 12 weeks after contracting COVID-19, and previously predicted there would be more than 1.3 million cumulative historical cases nationwide by the end of 2023. Government estimates also suggested that between 5 and 10 per cent of people who contract COVID-19 continue to experience symptoms beyond three months.

Australia currently has a small number of specialist Long COVID clinics operating through hospitals and general practitioners in New South Wales, Victoria, South Australia and the ACT.

Professor Paul Griffin from the University of Queensland School of Medicine said the absence of a reliable test creates real difficulties for patients. "It's a complex constellation of symptoms that can involve pretty much every organ system in the body," he said, noting the condition can also present differently across individuals and be confused with other illnesses that share similar symptoms.

In the worst cases, he warned, patients without a confirmed diagnosis risk having their symptoms dismissed entirely. "They may see some clinicians who say that they don't have anything wrong," Griffin said.

What This Means for Patients and Future Research

Researchers and clinicians are careful to stress that the Stanford findings do not invalidate the experiences of people who have suffered serious, ongoing symptoms. Those misidentified as Long COVID patients may still have been dealing with debilitating illnesses caused by other conditions, making accurate diagnosis more important, not less.

Griffin said refining the understanding of Long COVID is essential for improving outcomes. "We need to make sure that we continue to look into Long COVID, manage those people, try and find tests and obviously also therapies to try and improve their situation," he said.

It is also suspected that there may be distinct forms of Long COVID, which would further complicate both diagnosis and treatment going forward. The criteria used to identify the condition have already shifted among experts over time, adding another layer of complexity to an illness that remains, for now, without a definitive clinical marker.

For Australians navigating the healthcare system with ongoing COVID-related symptoms, the evolving picture underscores the importance of staying informed about what COVID health services and support are still available as policy settings continue to change.