Dutch researchers have discovered that persistent fatigue in patients with Long Covid has a biological cause –  their muscle cells produce less energy than those in healthy patients. 

“We’re seeing clear changes in the muscles in these patients,” said Michèle van Vugt, professor of internal medicine at Amsterdam’s UMC teaching hospital. The results of the study were published today in Nature Communications.

In total, 25 Long Covid patients and 21 healthy people participated in the study and were asked to cycle for 15 minutes. This cycling test caused a long-term worsening of symptoms in people with Long Covid, known as post-exertional malaise (PEM).

The researchers looked at their blood and muscle tissue one week before the cycling test and one day after the test. “We saw various abnormalities in the muscle tissue of the patients. At the cellular level, we saw that the mitochondria of the muscle, also known as the energy factories of the cell, function less well and that they produce less energy,” said Rob Wüst, assistant professor at the department of human movement sciences at the VU University.

“So, the cause of the fatigue is really biological. The brain needs energy to think. Muscles need energy to move. This discovery means we can now start to research an appropriate treatment for those Long Covid,” Van Vugt said.

One of the theories about Long Covid is that coronavirus particles may remain in the body of people who have had the coronavirus. “We don’t see any indications of this in the muscles at the moment,” said Van Vugt. In addition, the researchers saw that the heart and lungs of patients functioned well. This means that the long-lasting effect on a patient’s fitness is not caused by abnormalities in the heart or lungs.

“In concrete terms, we would advise Long Covid patients to be aware of their physical limitations and not to exceed them,” said Amsterdam UMC researcher Brent Appelman. “Walking is good, or riding an electric bike, to maintain some physical condition.”

Although the majority of people infected with the SARS-CoV-2 virus recover within weeks, a subgroup, estimated to be around one in eight, will get Long Covid, the research team said. 

The Netherlands has various initiatives underway into Long Covid, which has affected up to 100,000 people in the Netherlands. 

In December preparations began in the Netherlands to launch a major research project to find out if existing medicines can ease the symptoms of Long Covid.

The researchers will look at the impact of a large number of cheap, readily available drugs, such as Metformin, a medicine against diabetes.

 “Sometimes you then hear a drug works and that some people partially recover,” said Marc Bonten, professor of infectious diseases at UMC Utrecht. “But scientifically, so far it has not been proven at all to what extent such a drug does or does not work, or whether it is safe. We want to answer those questions with this project.”

The project is one of the initiatives applying for a Dutch health ministry grant for research into Long Covid. The government has set aside €32 million to fund such projects.