A recent research paper suggested their findings indicated a close link between nasal receptors and the immune system. The implication being that olfactory experiences were critical to staving off dementia over time.

Although many other interesting implications arise, one could be that the people who survived Covid but lost their sense of smell have a 'higher' risk of developing dementia.

[pubmed.ncbi.nlm.nih.gov]

Unrelated to the above is an as yet undocumented finding. Cannabis suppresses dream recall in some people. The finding is that use of the herb Entada Rheedii can significantly reduce the inability to recall dreams due to prior cannabis intoxication. This may be due to the bioactives of the Entada rheedii causing more elaborate and thus more memorable dreams.