, according to a new preprint study published on MedRxiv that hasn’t yet been peer-reviewed.
Long COVID has been hard to define due to its large number of symptoms, but researchers at King’s College London have identified three distinct profiles – with long-term symptoms focused on neurological, respiratory, or physical conditions. So far, they also found patterns among people infected with the original coronavirus strain, the Alpha variant, and the Delta variant.
“These data show clearly that post-COVID syndrome is not just one condition but appears to have several subtypes,” Claire Steves, PhD, one of the study authors and a senior clinical lecturer in King’s College London’s School of Life Course & Population Sciences, said in a statement.
“Understanding the root causes of these subtypes may help in finding treatment strategies,” she said. “Moreover, these data emphasize the need for long-COVID services to incorporate a personalized approach sensitive to the issues of each individual.”
The research team analyzed ZOE COVID app data for 1,459 people who have had symptoms for more than 84 days, or 12 weeks, according to their definition of long COVID or post-COVID syndrome.
They found that the largest group had a cluster of symptoms in the nervous system, such as fatigue, brain fog, and headaches. It was the most common subtype among the Alpha variant, which was dominant in winter 2020-2021, and the Delta variant, which was dominant in 2021.
The second group had respiratory symptoms, such as chest pain and severe shortness of breath, which could suggest lung damage, the researchers wrote. It was the largest cluster for the original coronavirus strain in spring 2020, when people were unvaccinated.
The third group included people who reported a diverse range of physical symptoms, including heart palpitations, muscle aches and pain, and changes to their skin and hair. This group had some of the “most severe and debilitating multi-organ symptoms,” the researchers wrote.
The researchers found that the subtypes were similar in vaccinated and unvaccinated people based on the variants investigated so far. But the data showed that the risk of long COVID was reduced by vaccination.
In addition, although the three subtypes were present in all the variants, other symptom clusters had subtle differences among the variants, such as symptoms in the stomach and intestines. The differences could be due to other things that changed during the pandemic, such as the time of year, social behaviors, and treatments, the researchers said.
“Machine learning approaches, such as clustering analysis, have made it possible to start exploring and identifying different profiles of post-COVID syndrome,” Marc Modat, PhD, who led the analysis and is a senior lecturer at King’s College London’s School of Biomedical Engineering & Imaging Sciences, said in the statement.
“This opens new avenues of research to better understand COVID-19 and to motivate clinical research that might mitigate the long-term effects of the disease,” he said.
A version of this article first appeared on WebMD.com.