Brain fog is one of the most pervasive symptoms of ME/CFS, and it can be a major debilitating factor. Brain fog can include short-term memory problems, inability to multitask, comprehension difficulties, language problems, and disorientation.
In the study, researchers monitored cardiac activity while participants performed cognitive tasks. They found:
- People with ME/CFS were slower than healthy controls
- Heart-rate variability was low and unresponsive in the ME/CFS group
- The heart rate was more reactive after cognitive challenges
- Heart-rate recovery was slow after cognitive challenges
- Heart-rate variability was an accurate predictor of cognitive outcome
Those cardiac functions are regulated by the vagus nerve. Dysfunction of the vagus nerve has long been suspected in ME/CFS, especially when it involves a symptom called neurally mediated hypotension (dizziness upon standing due to a sudden drop in blood pressure.)