Long COVID Risk Factors Revealed as Scientists Identify Two Distinct Illness Patterns
Nikhil Prasad Fact checked by:Thailand Medical News Team Jul 26, 2026 55 minutes ago
Medical News: Long COVID is not a single condition but appears to develop in different ways depending on a person's health, age, and the severity of their original infection, according to a new study by researchers from Kingston University London, Croydon University Hospital, and Bournemouth University. Their findings could help doctors identify patients most at risk and eventually tailor treatments to different forms of the condition.
New research reveals that long COVID develops in two distinct forms, with underlying illnesses, inflammation, and severe infection
driving the greatest risk.
Large Hospital Study Uncovers Major Risk Factors
The research analyzed 627 adults hospitalized with COVID-19 in London between February 2020 and December 2022. Of those patients, 252, or 40.2%, later developed long COVID, while the remainder recovered without persistent symptoms.
Researchers found that having existing medical conditions was the strongest predictor of long COVID. Even one pre-existing illness increased the likelihood by more than four times compared to people without underlying health issues. Older age, longer hospital stays, and higher fibrinogen levels—a blood protein linked to clotting and inflammation—were also independent predictors of lingering illness. Elevated fibrinogen suggests that abnormal blood clotting and ongoing inflammation during the acute infection may continue to influence recovery months later.
Symptoms Change Dramatically Over Time
One of the study's most striking findings was how symptoms evolved after the initial infection.
During hospitalization, breathing problems, cough, and fever were the most common complaints. However, by 12 weeks or more after infection, these symptoms had largely improved. Instead, fatigue became the dominant problem, increasing from just 7% during the acute illness to more than 32% during follow-up. Memory problems, which were almost absent during hospitalization, also became increasingly common, while nearly one-quarter of patients continued to experience shortness of breath months after leaving the hospital.
This
Medical News report highlights that long COVID is not simply an extension of the original infection but often transforms into a different illness dominated by exhaustion, breathing difficulties, and brain-related symptoms rather than fever or cough.
Scientists Identify Two Different Types of Long COVID
Using advanced statistical analysis, the research team discovered two distinct long COVID patterns.
The first was a fatigue-dominant form, where patients mainly experienced persistent tiredness and breathlessness with relatively few other symptoms.
The second was a far more complex multisystem form. These patients experienced fatigue together with memory difficulties, brain fog, muscle pain, joint pain, persistent cough, headaches, anxiety, and other symptoms affecting multiple body systems
. Surprisingly, younger patients and those who had spent longer in hospital were more likely to develop this multisystem pattern, while older patients more commonly developed the fatigue-dominant form.
Long COVID Risk Changed During the Pandemic
The researchers also discovered that the likelihood of developing long COVID changed dramatically as the pandemic evolved.
Patients infected during the original Wild-type and Alpha waves had long COVID rates above 50%, while the rate dropped sharply during the Delta wave to around 12%. Although the risk increased slightly during the Omicron period to about 21%, it remained far lower than during the earliest stages of the pandemic. The researchers believe this decline likely reflects a combination of changing virus variants, vaccination, prior immunity, and improvements in medical treatment.
Conclusions
The findings suggest that long COVID is driven by a combination of underlying health conditions, the body's inflammatory response, and the severity of the initial infection rather than by a single cause. Recognizing distinct long COVID subtypes could help doctors identify vulnerable patients earlier, improve monitoring after hospital discharge, and pave the way for more personalized treatments instead of relying on a one-size-fits-all approach.
The study findings were published in the peer reviewed journal: Biomedicines.
https://www.mdpi.com/2227-9059/14/8/1662
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