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Long COVID patients may experience different types and severities of lingering symptoms. Allison Shelley/For The Washington Post via Getty Images
  • A new study seeks to advance the understanding of long COVID.
  • It finds that long COVID can be divided into three types of conditions, depending on the type of symptoms experienced.
  • The authors of the study also find links between COVID-19 variants, symptoms, and long COVID’s duration.

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As experts attempt to unravel the tangle of symptoms and long-term effects of what is collectively known as “long COVID,” a new study seeks to provide some clarity.

Working with data collected in a health study app by personalized nutrition company ZOE, researchers from King’s College London in the U.K. have begun to discern some order in the chaos.

The study finds that long COVID can be grouped into three symptom-cluster types: neurological symptoms, respiratory symptoms, and systemic/inflammatory and abdominal symptoms.

  • Neurological symptoms — the most commonly reported long COVID symptoms — include anosmia/dysosmia, brain fog, headache, delirium, depression, and fatigue. (Loss of taste from COVID is typically attributable to a loss of smell.)
  • Respiratory symptoms involve possible damage to the lungs and include severe shortness of breath, palpitations, fatigue, and chest pain.
  • Systemic/inflammatory and abdominal symptoms include musculoskeletal pain, anemia, myalgias, gastrointestinal disorders, malaise, and fatigue.

For the study, researchers analyzed data for 336,652 individuals collected by ZOE’s COVID Symptom Study. Of this group, 1,459 reported post-COVID symptoms defined as more than 12 weeks after acute COVID-19 infection.

Dr. Jai Marathe of Boston University School of Medicine in Massachusetts, who was not involved in the study, told Medical News Today, “This study definitely improves our understanding of post-COVID syndrome and more importantly, who might be at risk of prolonged illness and debility.”

“Physicians and patients,” Dr. Marathe pointed out, “are both looking for answers regarding who is at risk for developing long COVID, how long symptoms will last, what will help resolve the symptoms, etc. While this study does not answer all these questions, it provides a strong framework to build on.”

The study, which has not yet been peer-reviewed, has been published on the pre-print server medRXiV.

The researchers were also able to begin to identify the symptom clusters associated with SARS-CoV-2 variants and with vaccinations.

Dr. Liane S. Canas, corresponding author of the study and postdoctoral research associate at King’s College London, told Medical News Today:

“Our results suggest that chest-related symptoms (respiratory cluster) in the U.K. population were more evident among unvaccinated patients infected by the initial form of the virus [referred to as the “wild” variant].”

“Differently,” Dr. Canas continued, “patients with either the Alpha or Delta variants have shown a higher incidence of neurological symptoms, such as anosmia and brain fog.”

“Unfortunately, we could not robustly evaluate the effect of vaccination for these two variants. For Alpha, we didn’t have enough individuals vaccinated at the time of infection. For Delta, we didn’t have enough unvaccinated individuals at the time of infection who developed long COVID,” she pointed out.

Systemic/inflammatory and abdominal conditions were lightly associated with all variants.

“On average,” said Dr. Canas, “the wild-type form of the virus has shown a longer prevalence of symptoms, 30 weeks when compared with Delta and Alpha at 24 and 25 weeks respectively.”

“However,” she noted, “since we only analyzed data from individuals with illness for longer than 12 weeks, these results are less significant than the profiling of the clusters, and would require further research, which would also consider the effect of vaccination.”

“The findings of the study,” said Dr. Marathe, “suggest that individuals struggling with long COVID, who experience severe shortness of breath, hoarse voice, loss of smell, fatigue, delirium, anosmia, headache, and fever were more likely to [experience] prolonged and severe symptoms.”

“Physicians armed with this information,” she said, “may be able to better counsel their patients and expectations for symptom improvement. They may also work towards targeted treatment approaches that address the symptom cluster impacting, and hopefully improving, clinical care for the patients.”

The authors of the study are still analyzing data related to the Omicron variants, but have shared some early insights.

Dr. Canas said, “Initial results have shown that the prevalence of long COVID among Omicron variant-infected patients is much lower than that of the other variants.”

An article about the research from ZOE says that the chances of getting long COVID from Omicron were 20%-50% less than from other variants, with Omicron cases representing just 4.4% of the cases studied, compared to the Delta variant’s 10.8% of cases.

Dr. Marathe cited other research into the relationship between Omicron variants and long COVID:

“Some studies have reported a lower risk of developing long COVID following COVID-19 infection with the Omicron variant compared to the Delta variant, while others have noted that patients who develop long COVID following Omicron variant infection have less severe disease. This is also true for the overall decreased severity of symptoms during acute Omicron infection.”

Even though a lower percentage of people with COVID-19 infections from Omicron variants develop long COVID, the strains’ greater infectiousness means that more people are being infected, and thus, more people are developing long COVID.

“While the overall number of patients with long COVID in the community may be lower, at Boston Medical Center, the number of patients seeking care in the long COVID clinic has remained steady throughout the post-Delta and post-Omicron surges,” said Dr. Marathe.

In terms of long COVID symptoms with recent variants, not much has changed, she said:

“We have not noticed a big difference in long COVID symptoms between the Omicron variants that were circulating during the winter and spring months. Fatigue, shortness of breath, mood disorders, and brain fog were still the most common complaints reported by patients with long COVID.”

Dr. Marathe regarded the new study as valuable:

“This may pave the way for additional research efforts to evaluate the different pathobiological pathways that may contribute to the development of long COVID, and help us define the condition more successfully.”

“I think we still don’t know who is at risk for developing long COVID and why they are at risk. As we increase our understanding of this disease, it will help inform strategies regarding treatment and prevention of long COVID,” she added.