As the delta variant of COVID-19 spreads and infects a growing number of fully vaccinated people, many take comfort in the fact that a breakthrough infection is likely to be mild. However, a mild COVID-19 infection is still quite risky. A growing body of evidence suggests that a mild case of COVID-19 can cause long-term brain damage, including:
For many of us, this evidence is hard to accept and does not match our experience. Most of us know someone who has recovered from a mild COVID-19 infection and reports no lingering symptoms. But even in these cases, damage may have occured -- the neurological impact of this virus is often mild enough to be imperceptible to the individual, at least initially.1
Still, though these effects may be subtle, they are measurable and consequential -- on average, people who've had mild COVID-19 perform worse on cognitive tests and show patterns of brain tissue loss that appear "strikingly similar to those associated with Alzheimer’s disease or other forms of dementia,"2 raising concerns that the "long-term consequences of COVID-19 may include these disorders."
Update: In addition to the studies covered below, the July 2021 Alzheimer’s Association International Conference featured an additional batch of new studies supporting a link between mild COVID-19 and cognitive decline.