Conditioned Pain Modulation Impaired in Individuals With Symptomatic COVID-19

Individuals with symptomatic COVID-19 were found to have impaired conditioned pain modulation (CPM), according to the results of a study published in the Journal of Pain.

Participants (N=59) with symptomatic COVID-19 (n=26) and asymptomatic COVID-19 (n=13), as well as those who had recovered from COVID-19 (n=20) were recruited for this study at the University of Florida from March to May 2021. The study participants underwent evaluation for CPM and exercise-induced hypoalgesia, as well as pressure-pain sensitivity testing and a battery of psychological and pain questionnaires conducted at 3 visits within a 7-day period.

The mean age of symptomatic, asymptomatic, and recovered cohorts was 21.6, 23.2, and 24.3 years, respectively; 61%, 66%, and 44% were women, respectively; and mean BMI was 25.5, 23.5, and 24.6 kg/m², respectively.

The recovered cohort reported having had COVID-19 symptoms of congested nose (80%), shortness of breath (72%), phlegm (68%), fever (60%), cough (60%), and hemoptysis (4%). The symptomatic cohort reported fatigue and headaches (84%), myalgia (72%), anosmia (60%), ageusia (56%), sore throat (48%), diarrhea (44%), nausea (28%), and facial pain (12%).

CPM scores of the leg (P =.008) and arm (P =.001) had significant group-by-time interactions. The magnitude of CPM differed in the leg (mean, 12.8% vs 33.8%; P =.014) between the symptomatic and asymptomatic cohorts, respectively. For the arm, significant differences in CPM scores were observed between the symptomatic and asymptomatic groups (mean, -1.0% vs 33.3%; P <.001) and between the symptomatic and recovered cohorts (mean, -1.0% vs 23.4%; P =.004).

A significant time effect of exercise-induced hypoalgesia in the leg was observed overall (36.1% immediately following exercise vs 20.8% at 15 minutes following exercise; P <.001).

One dimension of the questionnaire assessing pain attitudes was found to be different between groups, in which the asymptomatic and recovered cohorts differed for cautious self-doubt (P =.027). No group differences in any dimensions of the International Physical Activity Questionnaire, Paint Catastrophizing Scale, Profile of Mood States, or Pressure Pain Threshold evaluations were observed.

This study may have been limited by relying on symptom recall in the recovered cohort. In addition, the investigators did not evaluate for the presence of long COVID-19.

These data indicate that individuals with symptomatic COVID-19 experience CPM dysregulation. The investigators commented, “These findings are concerning in that normally healthy, young adults who have demonstrated only mild to moderate symptoms of COVID-19 have an impaired CPM response…”  It remains unclear whether long-term CPM dysfunction may contribute to symptoms of long COVID-19 or may predispose some individuals to develop chronic pain.