Post-Covid Syndrome: Acetylcholine Impairment That Responds to Nicotine?

Original title: "Is the post-COVID-19 syndrome a severe impairment of acetylcholine-orchestrated neuromodulation that responds to nicotine administration?"

It's a shame this particular study only had 4 subjects, however. I'm not super convinced this is a great treatment, in general, but, that said, this bit is interesting:

the cohort study of Hippisley-Cox et al. (2020), with a total of 8.28 million participants (including 19,486 confirmed COVID-19 cases), showing lower odds for COVID-19 infection and COVID-19-related ICU stay in association with smoking (Hippisley-Cox et al. 2020)

Tryptophan metabolizes to either kynurenine =>...=> nicotinamide (B3) or 5-HTP => serotonin.

Long COVID strongly affects the hypothalamic-pituitary-adrenal axis, suprachiasmatic nucleus, and other serotonin-regulating parts of the brain.

Wonder how B3 works for long covid..