A new study that is the first to compare inflammation and brain stress responses in long COVID-19 patients with individuals who have fully recovered shows that those with continued brain fog and other cognitive issues have a lower ability to adapt to stress and higher levels of inflammation in their brains.

The study shows that the SARS-CoV-2 spike protein remains in the brain's protective layers, the meninges, and the skull's bone marrow for up to four years after infection. This persistent presence of the spike protein could trigger chronic inflammation in affected individuals and increase the risk of neurodegenerative diseases.