A study led by researchers at the University of Oklahoma shows a connection between symptomatic COVID-19 infections and the ability of the central nervous system to respond to painful stimuli.
Christopher D. Black, Ph.D., associate professor in the Department of Health and Exercise Science, Dodge Family College of Arts and Sciences at OU, led the study with a doctoral student in his lab, Jessica A. Peterson. Peterson, the first author of the study, is now a postdoctoral researcher at the Pain Research and Intervention Center of Excellence at the University of Florida, Gainesville.
In late 2020, the scientific community began wondering what the potential long-term effects of COVID-19 infections might be. One of the common symptoms of COVID-19 infection is system-wide inflammation, which can lead to headaches and general aches and pains, also called myalgia.
“When you get inflammation, things that weren’t painful before now become painful,” Black said. “We realized we have all of these people who have had COVID-19, and there's a chance they may be at a higher risk of developing chronic pain conditions when they get older. We wanted to see whether people who had experienced a COVID infection – even though they no longer have symptoms – if they have normal function in their central nervous system in relation to their ability to ‘correctly’ respond to a painful stimuli.”
The study, conducted from January through March 2021, included 59 participants separated into three groups. The symptomatic group included those who had previous symptomatic COVID-19 infections that were confirmed through PCR or antibody testing. An unexpected addition to the study became the asymptomatic group – those who had not known they had previously been infected by COVID-19 and had not experienced symptoms but were confirmed through antibody testing. The control group had neither experienced COVID-19 infection nor had antibodies present at the time of testing.
The researchers measured each person’s pain threshold – the amount of pressure applied to a muscle, in this case in the participant’s arm or leg, that it takes for the participant to report feeling pain. Second, the researchers measured pain modulation, or the signals sent from the central nervous system to the brain and spinal cord that can “change the volume” on how much pain a person reports.