For how widespread it may be, very little is known about myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Up to 2.5 million Americans are estimated to have the chronic condition, according to the Centers for Disease Control and Prevention, and many cases seem to arise in women following an infection. Other than that, however, researchers have been at a loss to explain key questions: Why do symptoms vary so widely between individuals with the condition? Is there a foolproof way of diagnosing it? And what causes ME/CFS?
These questions are especially in the public’s minds these days thanks to the COVID-19 pandemic. Long COVID patients are currently struggling to have their symptoms treated seriously, and many people with ME/CFS have noted the similarities between their conditions and have helped organize and advocate for concerted research into both conditions.
Two new studies, both published in the journal Cell Host & Microbe on Feb. 8, now give us some answers by linking ME/CFS to the inner workings of the human body. The new research ties the condition to underlying disruption in a person’s gut microbiome—the bacteria and other microorganisms that live in harmony and conflict with cells in the gastrointestinal tract.
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Research into the gut microbiome has taken off over the past decade to explain both the causes behind and the impacts of all manner of conditions, from illnesses that affect the gastrointestinal tract to neurodegenerative diseases. It’s not a far stretch to look at the microbiome’s role in a condition like ME/CFS, which can cause gastrointestinal and neurological symptoms.
So given the growing body of research, the first study, though interesting, wasn’t all that groundbreaking. A team led by researchers from Columbia University analyzed stool samples from 106 people with ME/CFS and 91 healthy individuals. They found that ME/CFS patients had lower levels of a species of bacteria called Faecalibacterium prausnitzii than those without the condition. Moreover, the levels of this bacteria were associated with fatigue, with lower levels being tied to more severe symptoms.
The second study, however, led by researchers at The Jackson Laboratory, was much more intriguing. The team analyzed blood and stool samples from 149 ME/CFS patients and 79 healthy individuals. Unlike the other study,the researchers chose to classify the sick patients as either short- or long-term ME/CFS patients, based on whether they were diagnosed within the last four years, or more than 10 years prior. Julia Oh, a genomic medicine researcher at The Jackson Laboratory who led the study, told The Daily Beast in an email that ME/CFS can look very different for different individuals, and the researchers wanted to see if the ways in which the chronic illness presented in people had anything to do with its duration.
What they found was striking. Initially, ME/CFS was tied to temporary disruptions in the gut microbiome. Over time, the microbiome recovered, but other health and metabolism problems persisted. The researchers found that these issues were reflected in the individuals’ blood work, as well as their symptoms. Long-term patients had higher levels of cholesterol and more frequently reported fibromyalgia, constipation, and sleep disorders; on the other hand, individuals with a recent ME/CFS diagnosis tended to report poor appetite more frequently, which the researchers wrote is consistent with gastrointestinal disturbances.
Both studies are correlative, meaning these changes to the microbiome may not be causing ME/CFS symptoms but could in fact be a result of the chronic illness.
Still, Oh and her team have a theory about how all the pieces fit together. At first, a person with ME/CFS may lose beneficial bacteria and other microbes. Then, their out-of-whack microbiome “may have cumulative and long-term effects, where damage may be caused by an initial trigger, resulting in cascading events,” Oh said. Even when the initial disruption is restored, a person’s metabolism may be permanently altered. Now that a growing body of evidence suggests ties to the gut microbiome, researchers can study whether administering prebiotics or probiotics might help relieve symptoms and reverse metabolic changes for people with ME/CFS.
As there are no approved laboratory tests to diagnose ME/CFS, Oh said that she hopes her team’s method will aid in future diagnoses of the disease since it was highly accurate at distinguishing between patients and controls in the study. Still, she added, future research will have to compare the microbiomes and metabolites or ME/CFS patients to those with conditions that present similarly, like fibromyalgia.
Understanding ME/CFS will in turn shed light on other poorly understood chronic illnesses—both by identifying shared disease-causing pathways and by demonstrating the benefits of separating patient populations into short- and long-term cohorts.
“The approaches taken here could be taken in long COVID” to help scientists and patients find desperately sought answers, Oh said.
