One of the major consequences of the COVID-19 pandemic has been the significant incidence of persistent fatigue following resolution of an acute infection (i.e. post-COVID fatigue). We have shown previously that, in comparison to healthy controls, those suffering from post-COVID fatigue exhibit changes in muscle physiology, cortical circuitry, and autonomic function.
Here we present results of a longitudinal study, comparing correlates of fatigue anywhere between 12 weeks and up to 45 months post COVID infection. All participants (N=145) were suffering from post-COVID fatigue at the time of testing. While post-COVID fatigue is defined as ongoing fatigue 12 weeks or more post COVID, many people do show significant recovery over time. However, others still have ongoing fatigue 2 years or more post COVID. This study aimed to investigate neurophysiological differences within this broad timeframe.
We report self-perception of fatigue via questionnaires; as well as objective measures of cortical circuits via transcranial magnetic stimulation and reaction time tasks; peripheral muscle fatigue via twitch interpolation and nerve stimulation; and autonomic functions such as heart rate variability, oxygen saturation and temperature. Additionally, daily activity levels were measured with a wrist worn accelerometer (Axivity) over a period of 14 days in a subset of participants (N=108).