By Pat Anson, PNN Editor

People with chronic pain conditions such as fibromyalgia, chronic fatigue, migraine and irritable bowel syndrome are significantly more likely to have symptoms of Long Covid after a COVID-19 infection, according to a large new analysis.

Researchers at the University of Michigan analyzed electronic health records of over two million Americans and found that the risk of having Long Covid symptoms was higher in people with a chronic overlapping pain condition (COPC).  

Over half the patients (58.6%) with a COPC and a diagnosis of COVID-19 had symptoms of Long COVID, compared to only a third (33.6%) of those without a COPC.

“We hypothesized we’d see an increase in pain and fatigue because it’s something we’ve seen in the past with other infectious diseases, like the SARS outbreak in 2002,” said lead author Rachel Bergmans, PhD, a Research Assistant Professor at U-M’s Department of Anesthesiology, Chronic Pain and Fatigue Research Center. “A big predictor of future pain is having had pain in the past.”

Findings from the retrospective cohort study, published in the journal Pain, do not establish a definitive cause that links chronic pain with Long Covid – only an association.

It’s a bit of a chicken-and-egg situation. Many of the symptoms of Long Covid mirror those of COPCs – such as brain fog, chronic fatigue, headache and body pain – so it’s not clear which condition developed first. Interestingly, Long Covid symptoms were found in 24% of patients with a COPC who were not diagnosed with COVID-19.  

That finding could be explained by a relatively new concept in pain research called neuroplasticity or nociplastic pain – chronic pain that lingers and becomes heightened in the brain and central nervous system (CNS) long after the initial injury heals. 

“With nociplastic pain, some people have what you might call a pain setting turned up in their central nervous system. There’s evidence showing that infections, trauma, and stress can be a trigger for nociplastic pain features and related symptoms,” said Bergmans.

Nociplastic pain could also explain the cognitive dysfunction and other symptoms caused by Long Covid – known technically as post-acute sequelae of SARS-CoV-2 infection (PASC). The basket of symptoms now collectively known as Long Covid may have existed before COVID-19 even came along. In 2022, the CDC estimated that 18 million American adults had Long Covid.

“The onset of long COVID features was relatively common regardless of acute COVID exposure. In addition, those with pre-existing COPCs had an increased risk of being diagnosed with long COVID features. These findings reinforce the likelihood that nociplastic pain is a key mechanism in long COVID and can inform precision medicine therapies that avoid the pitfalls of viewing long COVID exclusively in the framework of infectious disease,” researchers concluded.

“For clinicians who treat people with long COVID, it may be helpful to review the medical record and see whether someone had a pre-existing COPC diagnosis before long COVID onset.”

Bergmans and all of her co-authors are either consultants or employees of Tonix Pharmaceuticals, a company that is developing new non-opioid treatments for fibromyalgia.