While only a tentative link for now, there's interesting indications that long-term cocaine abuse can be a cause for Alzheimers:
"Sig-1R binds to its ligand such as cocaine, resulting in dissociation of Sig-1R […]. The disruption of Sig-1R pathways has been implicated as causative mechanism(s) in the development of both neurodegenerative disorders such as Alzheimer disease (AD), Parkinson disease (PD), amyotrophic lateral sclerosis (ALS) and Huntington Disease (HD)."
www.researchgate.net/publication/315352441_Role_of_Sigma-1_Receptor_in_Cocaine_Abuse_and_Neurodegenerative_Disease