The primary findings of this longitudinal study are: (1) Among older people with MCI, smokers showed faster decline in functional performance compared to non-smokers; (2) Smokers demonstrated steeper decline in entorhinal cortex volume than non-smokers; (3) A history of cigarette smoking was not associated with change in CSF Aβ42, t-tau or p-tau levels over time at the prodromal stage of AD. This evidence concerns the gene MAPT and Alzheimer disease.